I think if she has told you as much, then, yes. She would probably end up leaving you. Maybe not for the first man that made her feel good again, but it could be him. Chances are that she'll really like being satisfied in bed and want it a WHOLE LOT!!
And I bet that when her going out and finding her satisfying sex starts taking presidence over any of your feelings and desires, thats when the real friction will start. The arguements, the finger pointing, the name calling....
Or perhaps she'll develope secret feelings for the man that can make her howl all night. Telling you nothings wrong, everything's fine, still love ya honey as she sneaks off to see him privately on the side. Then one day you find out they have been dating. Maybe even seen smooching by freinds or something, and when you confront her she says; I told you so, see what happened?