My girlfriend had previously asked me not to engage in online conversations (via Facebook) with a certain other girl because it makes her uncomfortable. This other girl is a sometimes friend/most of the time enemy of hers, but I can never fully tell since I see them together socially all the time and there appears to be no animosity. I agreed not to, but then the other girl started messaging me and I responded, kept up with the conversation, and even initiated conversation in one instance. I am really trying to figure out why. I have no interest romantically in this other girl, and am totally in love with my girlfriend, but I did like the attention from the other girl somewhat. What I'm wondering is why I did this? I'm not a cheater, I've actually been cheated on before, and I would never consider doing that to another person.

I disclosed this information to my girlfriend and she is now furious with me. She says she can't trust me anymore because I lied to her about this. I've apologized profusely, promised to atone, and promised to do whatever I can to earn her trust back. She won't see me in person and requested that I leave her alone until she decides to reach out to me. I feel like if I could just talk to her face to face then we can move past this, but the uncertainty surrounding the situation, coupled with her being angry with me, is absolutely eating me up inside.