I have a nano, I wear it in my pocket and I have absolutely no problems. I'm just careful, I can feel when there is light pressure on it. I have "friends" who say exactly that, bla blah, theyve have a friend whose friend's friend heard of one that broke in a pocket.. and I can tell they are just jealous.
I can't see that happening unless the jeans are EXTREMELY tight, or the person is really heavy, or extreme pressure was put on it against a flat surface or something.. the nanos, though delicate looking, thin, and (the polished front and chrome is) 'prone' to light scratching, they are in no way fragile; though treating them as if they are and being careful is worthwhile.
Even with all the supposed "problems" with the nano, most if not all of them are created by obsessive owners and jealous have-nots. I for one love my nano, and even though I have had some of that obsessive owner complex, I could not be happier with it and am in absolutely no way regretful.
The only damage done to my nano in the over a month I have had it is light scratches in the week of so before I got a full-body cover (the screen protector type) from Boxwave, which I highly reccomend. I'm probably going to pair it with the tubes, or an aluminum Core case, which I am positive will work out excelently.\
Give her the nano. She will love it.