Iphone backup question

I have a friend who insists on using a company computer to use her itunes/iphone. We have a person in the company who we know likes to hack everything, not because he is told to, but because he wants to prove he can. ( We know this, but have no way to prove it so lets just assume for this case that it's true ) A little concerned that all of her texts ( and therefore any texts I send to her also ) will be saved on her itunes backup, and can be hacked out by this guy. She doesn't believe all that is possible.

Just how vulnerable is she leaving herself by doing this?

 

Anyone?