<human>: Summarize the given text in a few sentences.

So hi. I'm a 22 year old guy and I can't say I've had much experience with dating or relationships, but I like to think I'm fairly socially competent and confident otherwise.

A girl I've been friends with since high school just told me that she's going out with some guy (who I don't know). Anytime before that, I don't /think/ I had feelings for her, but as soon as she said that I could feel my insides turn. Clearly I was bothered by it and clearly I must've had feelings at a subconscious level for her.

Now, here's where it gets tricky... We talk frequently, she's a good friend of mine. And I'm just not the type of person who can feign happiness. I'm trying my best to stay "me" but inevitably I'm not as engaged when we talk, I am not as open with texts, etc, etc. But she did nothing wrong, she obviously doesn't deserve this and I'm just not sure what to do here.
She's going to pick up on my vibe and eventually ask me. But if I tell her the truth, she's going to feel sad/bad and again, she did absolutely nothing wrong. So what can I do here? I'm really not sure...
<bot>: Girl friend told me she's dating a guy. It bothered me even  though I thought I didn't have feelings for her. Now what?