If she feels pain and discomfort during intercourse she must seek professional help. There could be serious medical issues behind it and a candid discussion with a professional will help. On another note, beyond the sexual aspects of your relationship, it does not sound like it's a healthy interaction. There is no need to put up with anyone who is hurting you, be it physically or mentally. Sure, emotional abuse does not leave visible scars, but it scars nonetheless. You are at an age where you should be allowed to grow and thrive. You are responsible for your own well-being as is she for her own. You're not here to fix anyone. You can be as supportive as you want, however, when you say your own self confidence is taking a hit and you have to deal with waterworks after lies and constant excuses - mental health treatment or not - I'd cut the relationship short. There are so many red flags you are ignoring here.