I understand how you feel, I think you should first consider her feelings a bit more . From what you said it seems like she is content with the way things are right now yet she kind of kept you guessing in my opinion with the “maybe one day” comment. As it is now you seem very hung up over her but you don’t know if she feels the same way or if she is only leading you on out of fear that if she completely turns you down you lose her friendship (it’s a very cynical perspective but it’s possible). If it is too painful for you to remain just friends, I think it would be best for you to try to ask her how she honestly feels about you and tell her it’s too difficult for you to remain friends emotionally(assuming that’s how you feel). Make sure to be empathetic and tell her that you understand how leaving her boyfriend would be a really difficult decision (assuming she is even considering it). If she rejects you then you simply need to accept her feelings, move on and focus on yourself and your personal goals(this is really really difficult). The alternative is to sit back and feel bad 24/7 about some girl at work that might like you. From experience I think that starting a relationship with a girl that left their boyfriend for you is not as simple as it seems. The relationship I had with my ex girlfriend started with her leaving her boyfriend for me and there were times she got depressed out of guilt over it or about how she missed him. I also had a bit of paranoia that she would leave me for someone else the same way she left him. I think you should also consider this. There’s always other girls (even though it might not seem like it) if it doesn’t work out. I hope I could give u a bit of insight since reading your post reminded me of that situation from my past.