What do you do when you think you love your best friend?

I have this one friend I've known for a year now named Kris and we stayed in the same dorm together freshman year. She had to leave abruptly to deal with personal issues and is going to a community college back home which is two hours away and she is with a guy now and her life is now in order. She still has moments where she relapses and I've helped her deal with stuff and vice-versa that has been hard for us to have gone through individually. She has become essentially my best friend. She told me lately that she's thinking of dumping her boyfriend or keeping it open because she feels like she needs to live. Last year she was someone I was about to ask out, but she left before I could. I don't honestly know what to do at this point.