Doesn't matter if the girl likes it or not, if she wants to keep the guy she should do it because otherwise he will go and get it somewhere else (probably fuck a hooker). So if the girl wants to keep the guy it's in her best interest to endure it if she doesn't want her man to cheat.
I read that in this book actually
http://www.amazon.com/What-Dont-Want...6435915&sr=8-1
That book is written from a man's point of view and explains how if a man wants something he WILL get it and if his wife/gf won't give it to him, he will get it somewhere else.