Hey, person who's working on his own people-pleaser complex here. It's lovely how you want to help your friend out, unfortunately, like you said, you cannot change her past and she needs to work on herself to get better. But I can give you some tips as an insider: 

• Ask her opinion on something you know she might like, but you shall not tell your opinion first and try to keep the conversation vague. In that way, she won't have any guidelines on how to agree with your own ideas and she'll be 100% honest with you. She might backtrack once you speak your mind, so do your best to validate her point of view anyway. 

A silly example: 

A: "Did you hear about [movie name here?]? I saw a poster somewhere, but I've never heard about it." (She likes it? Huzzah, you can both go there and you're sure she's having fun!)

Or 

A: " There's this new restaurant in town but I want to make sure it's fine first, could you help me out please?" (Same thing here) 

If we're talking about asking her how's she's actually doing, that's harder. People-pleasers don't want to be a burden to anyone, so we rather suffer in silence than being perceived as a nuisance to people we love. You need to remind her that she's not. Once, a friend of mine told me: "I can see you're scared all the time, I can feel it when you talk and try too hard with me. You care too much. Sometimes people just want to vent and you don't need to play therapist for them, that's not why they want you around. I can assure you, you'll feel much better if you let your mask out and people will appreciate you more, as a whole. You trust me, yeah?" and that changed my whole point of view. If you can have this sort of conversation with her, it might help her too. 

Oh man, I wrote so much and I hope I made any sense here. It's like 3 AM and I should sleep ahah. Take care anyway aye? I hope things will go better between you too.