Van, we agree but disagree.
From my point of view, she is not sexually frustrated; she is sexually unfulfilled. She gets off (which is her responsibility, not his) but she want more. She appears to be highly charged and seeks more than he can deliver at the end of a long day.
Were I in the counseling biz, I would suggest he encourage her to be patient for much longer foreplay sessions. Yes, as a young guy, he is impatient and wants to perform when he knows he can. That will improve over time.
He needs to extend the cunnilingus from 90 seconds to at least fifteen minutes. Get her off that way before coitus. As she appears to be able of multiple orgasms (once in bed, again in the tub), let her cum from his tongue and then worry about the penetration after that happens.
Lastly, maybe he needs to start a little earlier in the evening: fuck and THEN go fool around on the keyboard or bass. Hell, she's ready halfway through their watching stupid adolescent movies.
He's young and he will figure it out. As I said before, she really loves him (so it appears, to me at least), and will be patient. She also could be a bit more directive in letting him know he can move a bit slower.
I might be wrong. More often than not, I am.