Way too mad if my girlfriend checks out another guy?

About 5 months ago my girlfriend checked out a guy at a restaurant about 4 times and I asked her to stop when I caught her the first time. I was really pissed at the time but she apologized and we moved on. Lately, that thought popped in my head and I've been fighting with her ever since. yeah she shouldn't of done that but I know I'm overreacting. I'm debating breaking up with her over it. Has any of you ever had this problem?
Way too mad if my girlfriend checks out another guy?
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