Maybe you could go see a therapist to discuss the results of those tests you took. It could be you, too, have problems or something else. That would give you things in common with her. It's hard in relationships because at times the two people are at different places in life and self-discovery and more. You could try to relate to her as someone with problems just like you. I don't know what is taking it's toll on you because you haven't been specific. If she is sufferering from these illnesses she may need to just focus on getting better. You could just try to be friends and keep it on the lighter side if it's too intense for you. There is couples and relationship counseling, too. I know people who have benefitted from it. It takes time, like all worthwhile things. Sometimes getting away from it all helps me to see things in better perspective. Like taking a long drive away from it all by yourself. You need to take care of yourself first so you can function well. I hope this is of some help.