understand that you will be happy and live your life regardless if you are with her or not. who cares if she cheats, if she does she wasnt for you anyways. if she doesnt cheat then bonus
but really...it takes alot more effort to worry about her cheating then just accepting the fact that you really have no control over it so just go with the flow. if shes gonna cheat there is not a damn thing you can do to prevent it.
now just go out there and enjoy her.