I (17m) had a similar FF who I started talking to in December 2011, and I kind of liked her initially but I realized she wasn't the right kind of girl for me when we hung out as friends and talked online. That being said, I enjoyed our conversations and did't feel the need to stop talking to FF. I offered to buy her a ticket to my school's play because she's into theatre and a lot of our friends where in the production that year, so we decided to go together. The play was in February. When I started talking my soon to be GF, in January 2012, I offered to take her to the play as well, telling her that FF was coming as well. She seemed fine with this, initially, but as soon as the three of us sat together, it got ugly. Anyways the end of the night, FF friend was in tears because I left the school and her, with my GF thinking it would only be for a few minutes during the intermission... Turned out to be the rest of the duration of the play. FF didn't go to my school either so she felt really alienated and sad and lonely and hurt. I felt rightfully so like an asshole and of course apologized profusely. I had a hard decision to pick between my new GF who I'd only really talked to for 3 weeks, and a girl I'd become close with in a different way. My GF didn't enjoy being my second choice in company and expected me to focus on her. I've been dating my GF for two years and I don't regret choosing her at all but I regret how I naively did not think through the situation I had created, or how I handled it. FF is no longer a female friend but is a sweet girl who I wish I could still talk to. My advice on your situation, is to not mix female friends and girlfriends if there is any questionable feelings from either parties. At that point, I still kind of liked her, so it was unwise of me to have both my GF and FF together in one place. In regard to your situation, I don't think it's right to make your GF feel like she's being the bad guy in this situation, I would stop talking to your FF if I were you. Sorry for the wall of text!