Broke Bridesmaid

Buy her the dress, it's none of anyone else's business that you did so either. Also, if the other BMs gave you their budget and she didn't say anything then they clearly afford their own dresses. I look at it this way my nana use to tell me don't expect your money back if you pay for something for someone. And besides she is your close friend. I would do anything I could if I asked them to be in my wedding. So don't feel any type of way. Kind of sounds like you knew she was struggling before you asked. It's ok to help. The others don't need to know.

I'd just buy her the dress. I think that life evens out in the end and by the time you're both 80 the 50 bucks won't matter. When I do something like that for a friend, I say that. I just stress the value of that person in my life vs the money. I hope it works out for you!!

Double

I don't loan money, I would consider it a gift with no expectation of being paid back.

If she really wants to reimburse you could suggest she pay you back with a small piece of art for your home or wedding decor instead of the money if she wants too. Only if that is an option that you both would be okay with. Something she already has the supplies for like a sketch, a watercolor of your bouquet, a hand lettered sign for your wedding, whatever her talent is.