Should I give her condoms even if her mom said no to having sex?

My boyfriend and I are currently staying at his parents home. We’ve been dating for a while and throughout the years I’ve seen his little sisters grow from little girls to young women. I’ll cut to the point here.

About two weeks ago while we were watching tv, his sister tells me she wants to start using protection. She pretty much told me that she was getting intimate with her bf (unprotected sex) but they stopped because she was scared to get pregnant. She wanted to know if I’d buy her condoms. I kind of paused because, well... I was kind of shocked since I almost see her as my little sister. I asked if she spoke to her mom about it and she said yes. Her mom is 100% against the idea of any type of contraception because she doesn’t believe she’s “doing that” and even if she was she “needed to stop because god doesn’t want that” (paraphrased from what she told me her mother said).

So... what do I do? I told her I’d think it over but that she should listen to what her mom says. However, I was a teenager once because and I know that things don’t always stay pg-13 when you have a bf. I feel like she might have sex regardless and if she does, it’ll most likely be without protection. This isn’t really my business but at the same time she really seemed stressed about it. Any ideas?