I caught my girlfriend sending nudes to another guy, should I break up? What should I do?

Anonymous
This morning i caught my girlfriend sending nudes to another guy. This is my first relationship and i been with her for a year. Why did she do this to me? I treat her like a princess, i don't get get it. I got very mad and was going to leave her house asap. She was begging me to stay and talk about, so i did. She said sorry some many time and was crying and said "i don't want to lose you". I was still mad and when i asked her why you did this? she said "it was a one time thing, and i wll never do it again". She even gave me her phone to check , i didn't even check cause i was so mad and i got up and left.

She keeps calling and texting but i won't answer. I'm not sure about breaking up with her, my trust is lost though. What would you do in this situation? Should i trust her again?
I caught my girlfriend sending nudes to another guy, should I break up? What should I do?
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