Prevention and common sense are the best defense. Also for females to prevent purse snatching and pick pocketing- a crossbody bag with the flap turned into the body or better yet under the coat.
That tiger lady gadget reminds me of Wolverine from X-men.
Of course on the prevention and common sense stuff. That is definitely not lacking in this situation nor is world experience. 
Hmmm… I wonder if we’re listening to the same afternoon radio shows? 
I used to have to walk home from the subway through an iffy neighborhood late at night. I would put on my best jock walk. Think of it as a “I’m a tough m.f.er and I will damage you if you so much as look at me!” The idea is to take up a lot of physical space and not present yourself as a victim. I don’t think of @ucbalumnus’s suggestion as facetious. Wearing cute tottery shoes can mark one as easy pickings.
The best defense is awareness of your surroundings. The problem with something like pepper spray is that you need enough time to get it prepared in order to use it and that’s not usually practical. Imagine fumbling through your purse, having to find your spray and take off the top or release the safety, make sure it’s pointed the right way and spray it accurately into the eyes of a moving person, all while trying to monitor what your potential attacker is doing and scope out a safe place to run. You really need to practice the use of such things on a regular basis in order to be effective with them. I think self defense items can also give people a false sense of security.
I would get the person in question a safety/self defense class like the one @m0minmd describes.
I get everyone’s points and sincerely and truly appreciate the thoughts behind them. :x
Let’s assume the person is covering all the bases (because they are/have been covered) - being conscious of surroundings, has taken a self defense class (although a refresher wouldn’t hurt and is a good idea), is wearing sensible shoes and is physically fit and exercises regularly to maximize their running speed, not wearing headphones, is walking like a badass when alone, is making an attempt not to take unnecessary risks…
…if you have other ideas for personal safety devices, I’d love to hear about them. The idea is not to use them to replace all the sensible advice and therefore be less on guard but to potentially add another layer just in case.
I do like the idea of a personal alarm system mentioned by @MAB222. I agree about noise as a deterrent.
You caught me out, @teriwtt
OK, now I am curious as to what afternoon radio shows you all are listening to!
I would like to know which pepper spray devices work well. Of course one should be aware of surroundings and not wear tottery shoes through an iffy area. The idea is not to fumble through your purse for your pepper spray after the start of an attack, but to carry it in hand with your finger on the trigger as you are walking from the scary subway to your apartment, aware and ready to defend yourself. It isn’t only for girls with open purses in “tottery shoes”. My son will have to walk from a bus stop to his dorm in a not-great town at night too. Most of this advice (run! look mean!) doesn’t really help or answer the question at all. Does anyone out there have a pepper spray that they trust and would recommend? One that would shoot several feet away?
Back in the 70s I lived in a fairly rough part of Chicago. It was popular to have a whistle on your key chain and carry your keys in your hand whenever you were out. Well . . . I started to have all sorts of dreams about getting attacked and blowing my whistle and no sound came out. I’d wake up hyperventilating. After a few weeks of that, I got rid of the whistle. Never had that dream again. (and never got attacked)
@redpoodles: Your son is probably safer without the pepper spray. Pepper spray is a weapon, which means that it requires training to use properly in high-stress situations. It also greatly ups the stakes, so if used improperly (which is likely) it may greatly increase the danger, such as by inducing an attacker to also use a weapon. Walking around, amped up, hand on a weapon is a good way to assault a stranger and invite the associated legal trouble.
You should probably remember that despite media cries, we actually live with the lowest crime rate in modern history. People are a lot safer than they think they are.
Wellesley gives every incoming student a whistle. People take it very, very seriously. My daughter says that when anybody hears one, they call the campus police and run toward the sound of the distress. I imagine having a herd of pissed off Wellesley women running toward you would be sufficient to scare off most attackers.
I think the best way to stay safe is to trust your instincts. If someone makes you nervous, don’t reassure yourself, figure out why and deal with it. Go into a bar, restaurant, gas station, whatever. Don’t talk on the phone obliviously. Pay attention to who and what is around you. If you turn and take a photo of someone who’s walking behind you, they know you’ve seen them. Walk tall, wear shoes you can move in, be prepared to yell (and yell “call 911” and “get away from me, you creep!” and other specific things). Be aware that if someone grabs you, you should grab one fingers and pull it back as hard as you can–even a weak woman can break a finger that way.
@massmomm Wellesley is a very safe campus in a very safe town. My D goes there too and there is no need for anything more.
@Demosthenes49 “You should probably remember that despite media cries, we actually live with the lowest crime rate in modern history. People are a lot safer than they think they are.” You have NO IDEA what the crime rate is in this area I’m speaking of. NO IDEA.
To the OP: Go to the local police station and they may set you up or give better advice than is here on this board. Ours did.
Phone number to a good realtor who can move you to a better area! 
Sometimes the kind hearted among us service people who have no choice but to live where they do.
@fractalmstr You seriously said that? And with a winky? 8-| 
[-X
It was just a light hearted joke. There are many good recommendations in this thread already, I didn’t really have anything serious to add.
What about a mini air horn that people use at sporting events or carry on a boat? They are extremely loud and would get some attention .
I had a friend who was mugged (beaten up quickly) in Newark going to his car, decades ago. He was a very tough fellow in great shape, and with combative sport skills. None of that mattered because he didn’t hear them coming up on him, they outnumbered him, and they weren’t interested in seeing who was faster or the better fighter. They didn’t fight fairly. I don’t think sexual assaulters have any more sense of allowing a level playing field so you can use your protective devices.
Those people who perpetrate random sexual assaults and robberies are experienced at this stuff, and you aren’t going to get a chance to do much. I think a whistle could help, but I have grave misgivings about the fighting back advice, especially the ones involving sprays or the tiger claw stuff.
I’m in the avoidance camp.
Yup, dadx. A judo Olympic medalist was robbed on a beach in Rio just a couple of weeks ago.
I used to run on a trail by a river. Parts of this trail feel like running through wilderness, especially early in the morning when no one is around. Even though this is a very low crime area, stuff does happen. Not so long ago, a woman got attacked on the trail, and the assailant escaped. When I am running on these parts of the trail, I make sure to be fully aware of the surroundings - I do not have my ears plugged with earbuds. In case a creep appears out of the bushes, my plan is to try to escape by running or to jump into the river - I doubt the creep would want to be involved in the commotion. I can swim and have my iPhone in a waterproof case.