If you are a strong personality and can give a girl something that other men cannot, then her desire to change will be minimal.
Before entering into a relationship, it would be good to know about her past. Carefully find out how she feels about infidelity and whether she had such a thing in her life.
You must have a trusting relationship so that she can easily tell where she is and what her plans are.
Never create prerequisites for cheating (for example, do not send her on vacation to another country with a single friend who just broke up with a boyfriend).