Not sure what to do..?

I moved to this town, about 4 months back, I'm 19 years old, and got a serving job at a local place. A girl I work with, fit's my "type" perfectly. The first day I met her, I called my best friend and went on and on about how perfect she was compared to any other girl I've ever met. Now, 4 months later. We've been hanging out everyday even though she's been in a relationship for 3 years. Her boyfriend and me are extremely close friends and we always all hangout together with our group of friends. The other day I confessed to her, that the more we hang out, the more I start to fall for her. She's not in the BEST relationship, she has a lot of issues that she's afraid to address with him, because she's either embarrassed or frustrated, but she'll tell me. She's my best friend. She's told me that it's unfair because she feels like she can't have feelings for me because of her relationship, and it's extremely hard to not like me because we get along soo well, and that she can't help the fact that she wants to spend everyday with me because I make her happy, and make her feel better then her boyfriend does. I'm falling for her each and everyday, and I've told her, I'm not trying to ruin anything between any of the 3 of us, and I just wan't to see her happy, with or without me, we'll still be best friends. But, she's terrified to talk to her boyfriend and resolve the issues their relationship has, which hurts me, because she's suffering. I don't know what to do.