Hey couldn't find anything similar in the search so be gentle.

My girlfriend is currently on an itinerary with my Onepass number. I can see it online and change seats and everything. I thought nothing of it until I tried to do the same with my friend's trip. She flies so infrequently that she doesn't even know what a frequent flyer program is. So she offered to let me have the miles and Continental wouldn't let me apply my number to her itinerary. Upon reading the rules, it states only I can earn miles for my Onepass. Is the situation with my girlfriend a glitch or is it allowed and I just don't know how to do it properly?