Celica, I was on Androgel for nearly 9 months because of a skin disorder. I used a whole packet every day during that time. My sex drive went through the roof in a matter of two weeks.
Not only that, I was able to lift more, became a more aggressive/outgoing personality, grew hair on my face like crazy (now getting laser treatments to have it removed) and my voice became deeper. In fact, my voice has never returned to normal and it still cracks when I talk fast.
My doc was very nervous about the adverse side effects and took me off immediately when he thought they became too much. However, for my condition I was required to take a full packet and the side effects were considered a little extreme regardless.
I would have to agree with Ulter though. I now know full well what it feels like to be a man, hormonally-wise. I am in no way qualified to give advice as far as what dosage your girlfriend should take - but she should be prepared for the possible sides.