Are you sure you really need to know those things? Or are you really just curious to validate some negative suspicions you have and reinforce some negative feelings about yourself? You've said several times recently you're not feeling exactly happy. Asking those questions from your present emotional outlook/perspective sounds like you're looking for a way to further validate or feed negative feelings about yourself and possibly about your mom, too. As I recall, 15 is an emotionally loaded enough time on its own.

Don't get me wrong. They're valid questions. I'd be curious, too. I just wonder if they'd be better saved for another time when you're feeling better about yourself and when, if she were completely honest with her answers, you could better handle what you found out. I strongly suspect that part of why your mom has evaded the questions till now is that she doesn't think you're ready for that information, either, and isn't comfortable examining her own feelings about that time. I say give it a few more years when you're feeling steadier yourself. Also, then you won't be looking at the answers through 15-year-old eyes yourself.

You're a smart girl. I suspect if you think about it for a few minutes and put yourself in the position she was in 1991 or so, you can pretty well figure out the answers on your own anyway.