This woman sounds like a powder keg of insecurity ready to explode. She is insecure about telling the truth because it might end the relationship. She is insecure about her general appeal, attractiveness and self so she seeks validation from other men to fill that hole. It's good that she recognizes that, but what does that mean for your relationship? At which point do you say, 'Honey I understand that you feel insecure, but you feeling insecure makes me feel insecure about us'? I think there needs to be some kind of a mutual recognition that this is something that can sink the relationship and some serious steps need to be taken to address and resolve her issues.
Don't cry, don't regret and don't blame
Weak find the whip, willing find freedom
Towards the sun, carry your name
In warm hands you are given
Ask the wind for the way
Uncertainty's gone, your path will unravel
Accept all as it is and do not blame
God or the Devil
~Born to Live - Mavrik~