How does you suppose George is going to stop men from lilting the other characters?

You don't. It is easier to be a great boyfriend thereby keeping her from going after other boys.

At the beginning of the book they are goin to a ranch just south of Soledad to find workThey are running away from a town called weed

George Milton and Lennie Small, two displaced migrant ranch workers during the Great Depression in California.At the beginning of the book they are going to a ranch just south of Soledad

Unfortunately there isn't an easy answer to this; there isn't much you can do. Be with her, act assertive around the other guys, and try and make it obvious that you are together. If someone does...

Well....ask her, maybe tell her that disturbs you.