What should i do or say about this?

Me an my gf have been together for almost 9 months now. We always tell each other how much we love one another. How we wanna be together forever an everything. Well last night she accidentally sent me a text saying "if we didn't stop talking then me an nate woulda nvr gotten back together �n me an Cory would be dating or still talking" an I was like ok ok. Ik they use to talk an everything. I don't really like Cory but he's ok. So today she's acting different an says she feels guilty or something cuz I guess her an "Cory" always talked about dating. I say ik u two are Just friends an if u guys talk or maybe hangout everyone ina while then I'm ok with it. Cuz I'd nvr tell her she couldn't be friends with someone. But now that ik they always thought they'd date it kinda scares me. I trust her with everything an she tells me that she would nvr cheat on me or jeopardize us an "Cory" would nvr do that either. I believe her. But why do I still feel like crap...