You should have resolved this issue before you married her.
Her actions at that time were emotional and perhaps not logical. No amount of interrogation by you will make those actions and reactions by her will seem logical to you now.
No once a cheater is not always the case. However cheaters many times feel shut down in the relationship and communication become limited and difficult. I am no way condoning cheating but this is my observations from friends.
If you continually doubt her your marriage will not be happy for either of you.
The Leftists have left us!