Sorry for spelling errors.

Is there any change that my girlfriend of 3 years would cheat me or should I just forget this.

We were drinking at my friend party saturday and I was talking to
people when my gf was sitting next to me and writing instagram messages
with someone. I got a sneak peak that she was messaking with a guy (not a
big deal, didin't give it more thought) but everytime I turned to talk
to her she quickly closed the phone screen like she was clearly hiding
something. After we got home I told her I got jealous about her behavior
and she admitted that she talked to some past hook up of hers. I asked to show me the messages between them and she shew me but she first tried to hide the last ones but I busted her. The talk between then was pretty casual at first but the end was like this:

Other male (OM): Come somethimes to my caracan?... Oh, nevermind you already have a man.

F29: haha, yeah. I can't but good proposiotion.... Or I don't know it the caravan so good a place.

OM: That's all I have right now

F29: Well, I keep it in my mind. ;)

OM: You do

F29: I think you probably will find a better company

OM: Well it's not that easy to find someone to come in the caravan. But keep the proposition in mind if you are interested.

F29: Okay, I will. Good night....

F29: Would you still be interested ;) .... maybe the caravan won't be that interesting.

OM: I'm intetested"

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That's all she shoud me. I haven't asked did the conversation ended after that I busted her.

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Should I be worried of her cheating or just let it pass? We talk about it and she said she was sorry and did wrong playing along with him.