Ditto on agreement. The #1 question is does she
want to add muscle? SO many girls (though not on these boards) WANT to look "skinny and wimpy" because it's considered fashionable by people who don't know any better

. Maybe she's just going to the gym because you're there.
It's true what VG said about 70% of gym members just going through the motions. The sad thing is many really want their bodies to change, but they keep doing the same workout day in and day out and never challenging their bodies. Then there are those who think just by virtue of being IN the gym, that their bodies should improve.
Saying she does want to add muscle, she'll need to train with enough intensity to challenge herself. It takes challenge to change the body. She doesn't need to lift a long time (I rarely lift more than 45 min, except legs @ an hour). At the end of that time, I'm spent, but it's a good spent.
If her diet is lacking in nutrients and/or calories, it won't matter much what she does in the gym. Many women make the mistake of undereating and overtraining, and no matter how much hard work is done in the gym, the body can't get stronger and better without the right nutrients going in.
If you can tell us more about how she's currently training and eating, we'll be more help.