I do 3x12 or 5x5, for everything else I do cluster training, I don't take biceps seriously, shit's useless.
You're obviously afraid of squatting, because you're not doing it. There is no reason on Earth a person with access to a spotter, barbell and a squat rack should not be doing squats, barring a mobility limiting leg injury.
It's 150 lbs, she's a 140 lb volleyball player. You've probably got a good 30 lbs on her, oh wait, you have no lower body mass because you don't squat.
I just turned 17 on the 11th, been training seriously for about a year, before that just with my football team.