I agree. It's natural to be hormonal, to have sexual urges and desires. It's also very normal for GIRLS to feel that, although our society seems to look down on it as improper. HOWEVER - he is not respecting her values or feelings.
She should not be with someone who makes her uncomfortable. I dated someone who was ready to go further than I was and it made me feel uncomfortable. It didn't work out. Even if she gives in, the experience won't be a positive or healthy one for her; she will likely regret it, feel used, cheated, etc. It's really hard when you are pressured by someone that you like. When you want that someone to have a really great opinion of you. In young dating (or any dating really) there is that fear of rejection and sometimes we let that rule our decision-making.
Let her know you don't want to do something she regrets, that you don't think he will change. That you feel it's better for her to cut her losses and move on before the situation gets worse with him. Let her know you hate seeing her unhappy and you worry he will only make her more unhappy.