I'm struggling with a problem. I feel like I cheated on my girlfriend.
You "feel" like you cheated? So you didn't actually cheat?
The feelings are there. I afraid of the consequences  if I act upon them.
Cheating is something that happens all of the time. Cheating is bad for a relationship, it is better to stay  loyal and work on things instead. Staying  away from the person you want to cheat with helps.
I don't want to cheat. It would devastate my girlfriend.
It's good to hear you're concerned about your girlfriend's feelings. It would be best to avoid contact with this person. Your feelings for the other woman will likely fade in time.