Thanksgiving Dump? I have heard it called the Turkey Drop!
Never trash talk a bad girl/boyfriend. Or platonic friend for that matter. Instead, very gently, subtly, and, if need be, passive-aggressively, contrast the bad friend’s behavior with what an actual good friend would do. Your goal is subliminal influence. You want to plant seeds of doubt about the bad friend, but also to show what your child should be expecting from a partner or friend. Over time, this approach helps them to make better choices.
I really object to calling the girlfriend immature and vindictive. That’s the OP’s opinion but I’m sure the son doesn’t feel that way, and I’m sure the girl’s parents don’t feel that way. These are two kids. Kids fight and break up, get back together and it doesn’t make either of them bad or even immature (unless you feel all 17 year olds are immature, then I might agree).
I think the mother should ask for the stuff back. Girl is probably scared of OP and she’d just give it back.
But I’ve spent the day watching the hurricane. It’s very likely I’m going to lose everything as my household is in a flimsy storage facility in Florida. Yep, the stuffed animals, the Dorothy dress, the pictures all likely gone. And we will survive. Even my kids are fine with it although they would like to have their Brownie vests with all the patches, their Christmas stockings, even their prom dresses. I’m remarkably calm about it. My kids are safe and that’s what really matters.
Stay out of it as much as possible, but be supportive in moving forward.
When my D was destroyed by a breakup while at home with me, I wanted to yell at my D’s ex, call his mom on him, and many other fantasies. I felt almost as heartbroken as she did - because it was unbearable to see her so upset.
I didn’t do anything except be there for my D. I never bad-mouthed the ex, fully expecting he could end up back in the picture. Even though the breakup was bad, the guy still had good qualities that didn’t go away. I did as @Massmomm mentioned, and talked with D about the behaviors that are typical of a solid person, and what type of person she deserved. She did move on a little, and even dated several other guys.
(And then, yes, they got back together. For the third time. And they’ve been together again for a year- bringing the grand total to 4 years.)
My family was VERY careful never to get involved when I broke up with any of my boyfriends, even tho I dated each them quite seriously for several years (including some premarital counseling). I’m glad they stayed out of it, as I don’t think anything good would gave cone from them being involved at all.
Obviously there was some good and bad in the relationship. If your child wants specific possessions back, he has to ask. If he’s unable or unwilling, he has the option of asking you or someone else to ask, and at that point you can decide if you want to be “monkey in the middle” or not.
From the OP’s description of the girl’s actions, she sounds very immature for even a 17 year old. And threatening to throw his sentimental stuffed animal in the trash isvindictive. The fact that her parents wouldn’t see her as such isn’t very relevant.
I think the girlfriend sounds immature and vindictive! I’m said much worse about some of my kids’ exes.
A painful breakup or divorce which your child has to endure feels like it is happening to YOU!