I'm going to be completely honest and say that the education you will recieve at BMC is going to be better and more personalized than the one you would recieve at BU. If anything I think BMC will increase your chances of getting into med school. They are a top feeder school and I don't think the fact that it's an all women's college will make any difference. Don't get me wrong, BU is a great school, but it's obviously huge which could be a plus or a minus depending on what you're looking for. At BMC the student to faculty ratio is 8:1, meaning a lot more individual attention. Plus, you have to option to take classes at Haverford and Swat (which I'm sure you already know). And even though the U.S. news ranking can be random sometimes, they rank Bryn Mawr, Swat, and Haverford as the top three liberal arts colleges in PA. BMC is #23 overall and BU is #60 for national universities.
BMC is known for amazing academics and having a degree from bryn mawr really means something in the job market. I understand your dilemma, especially with wanting to be near your parents, but from what I've read about BMC, it seems like an incredibly supportive community. I hope visiting this weekend will help you make your decision! I'll be there too.