Can you help me get her back?

My best friend wanted to be offline for awhile and when she came back online she didn't answer to my texts but I was able to reach her somehow and I knew something was wrong so I asked why but she said she didn't want to talk about it and it seemed like she was trying to avoid me but after a long time I was able to reach her again and she told me that its because she has fallen in love with me but she couldn't say so because she knows I'm in love with someone else (someone who was away for years that I still tried to contact her but eventually I asked for advice and they all told me to give up on her so I did) so she then got a boyfriend and he somehow knew that she's in love with me and told her to block me even though she couldn't, before I knew she was in love with me I felt like she wanted to avoid me so I told her to text me when it's the right time, I got sick of waiting and I got her to tell me about everything but now I don't know what to do, I don't want to ruin their relationship by being with her(her boyfriend think I want to steal her away from him but I wouldn't do that and I don't know if I actually love her as a friend or more)yet I cant live without her... isn't there anything I can do to solve this? Like convince her boyfriend or something... I cant live without her but I don't want to ruin her relationship either