AITA for going out to have a coffee with someone my girlfriend is jealous of

I 26 M have a girlfriend 30 F. I love my GF even though we have a complicated situation that we have to be together secretly. She is jealous about my coworker and is vocal about it. I have no girlfriend before her and I like to think of myself as a loyal monogamous guy but she is still jealous of some people in my life.

I think if this coworker as a friend and kind of envious because he is good with his job and I guess nice because sometimes helps me.

Lately my coworker wants to meet up and have some snacks and I did blew him off multiple times because I know my gf doesn't want me to. And I can't really tell him because of our complicated situation of my GF. Yes, the coworker is a guy. And even though I know I am straight and no plans of going other way it doesn't put my GFs mind at ease.

I don't like for the coworker to think that I am avoiding him. ( Honestly I kind think that it's awful to force your significant other to cut people off and I don't want to cut other people off because they did nothing wrong to me ). So I agreed to have a coffee out. And we talked briefly caught up with work shit and I fled early because I have tutorial gig.

After that I felt guilty for what I did and told my gf right away. And her reaction is awful. She cried and I don't know what to do.