My girlfriend told her ex that she loves him, what should I do?

Me and my girl have been dating for almost a year, we have both expressed deep feelings for each other. We have both said that we love each other, and we want to get married But over the last few days, things have changed. I have been working all the time and I haven't been able to talk to her, and over the weekend she left her Facebook logged in to my computer. I'm not going to lie I was curious and looked at her sent messages, and two days before she sent a message to her ex saying that she misses him and loves him, it was a really deep message. I feel destroyed, and I don't know what to do, and I feel like I can't confront her about it, because I was dishonest in getting the information. I love this girl so much. Please help me
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+1 y
I recently confronted her and she denied even talking to him. She said that I needed to trust her. Then I told her I knew that she was really talking, she became real defensive, and started accusing me of spying and not trusting her.
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+1 y
I want to break up with her, but her brother is working on my car and I don't want her to go crazy and destroy it.
My girlfriend told her ex that she loves him, what should I do?
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