Should I dump her?

My girlfriend felt abandoned when I kept ignoring her phone call and then I lost my phone and went to a girl (just a friend's house) I ignored her call because I didn't want her to come to the house party I was at with my guy and girl friends to bring me back to our house.(I hated that house, I can't stand her kids). She freaked out and thought we were done... so she decided to activate her Facebook dating and chat with a guy. I came home several hours later, told her what happened (that I didn't cheat ) and that I had lost my phone. I found her messages on the dating site when she left her phone in the bathroom. I confronted her about it and she says she didn't cheat and started blaming me.
Should I dump her?
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