<human>: Give me the gist of the text in a nutshell

Hi guys, I'll just start off with my story.
I'm 22 and there's this girl I met a month ago (shes 18), we talked on and off and finally decided to meet last saturday. She invited me to hang out with her because I told her that I liked her and wanted to ask her out before, but wanted to wait a bit because I didn't want to get in between things with her good friend (who is in love with her) which she really adored. 
She said that she thinks I'm great because I wasn't just being a ass who only thinks about himself and not others.
We both had a great time together and I didn't have that much fun with a girl since like forever, it's probably been like 1 or 2 years actually. 

Problem being: She has a boyfriend now, she's with that friend of hers. I know that she doesn't love him, but they were friends for a while and she's hoping that she feels the same way like he does about her some day, that's why she tries to date him now, which is bulls*** imo because stuff like this usually doesn't work out, you just end up hurting that other person.

Anywho~ the girl pretty much knows, that I like her and would that I would love to get to know her better, problem being: 
I don't know how to approach things. I'm pretty sure that she will dumb him someday, but I don't want to wait for too long, it's just not worth waiting for someone without having full closure about the situation.
I also asked her if she would've gone out with me, if I asked her sooner, which she said yes to. I think she really likes me and I also think, that she finds me attractive, at least she told me that I'm good looking etc.
So what do you guys think I should do? Should I just tell her how I feel about "our" situation or should I rather wait.

I don't want to be the guy who sabotages relationship but I also don't want to lose her. Any advice is much appreciated. :)
<bot>: Met a girl, we really had fun together. But we both knew that it wasn't a date because she's in a relationship now. Want to date her, but don't know what to do.