Wow, I so have to wonder what kind of relationship your gf has been in recently but it worries me that her son has picked up these kinds of traits. A lot of stuff like this isnt just out of the blue - he too will have seen it somewhere and picked it up much the same way you are worried yours will.

It does sound like that yes she really needs help with it and is no doubt heart broken at the loss of a nice close relationship with her son.

There really is no easy answer. Sometimes the best way to handle a sticky negative is to try and make a positive. Such as offering to help her find her own place and some stuff for it. Then she will feel that you are helping her, not tossing her into the too hard basket.