Would you break up with someone for this reason?

I have a feeling this is going to be long but I’ll try and explain it as quickly and succinctly as possible.

I’ve been in a relationship with this woman for about one year. For the most part things have been good. The only problem I had was that I feel she has a tendency to be too “flirty” with other guys. I confronted her about this months ago, and to her credit, I noticed a change. However I still would see her doing it sometimes and when I would call her out on it she would accuse me of overreacting.

Fast forward to last week. She was using my computer and then went to take a shower. I went on the computer and she had not logged out of her email and I noticed an email from a dating website. I went the website and searched her profile. It had a picture of her, described her as single, and she even admits in the profile she enjoys being flirty.

I confronted her and she told me she had created the profile after a bad argument we had. She said she enjoyed ‘seeing who views my profile’ but had not made contact with anyone from the site. She offered to let me look at her sent email folder to prove this. In my view the fact that she made a profile for herself that describes her as single is bad enough. Also the fact that she describes herself as enjoying being flirty means she was lying to me all the times she said she wasn’t. Now I know some people don’t care if there SO flirts with someone, but I do, and have made that clear from the start.

She apologized and told me she felt terrible and deleted the profile. She swears she will “make it up to me and prove to you that I want you only”. I really don’t want to be in a relationship with someone who can’t talk to members of the opposite sex without flirting. She swears she will change. After finding the profile, can I trust her? Am I overreacting?