One thing that might help you? I doubt the guy will be allowed to ultrasound the individual women, just the two of them in private? There will be other women there and/or the teacher, etc.? Too, the machine will be on her breasts, not the guy's hands and he'll have to be looking at the monitor, not her breasts to see what he's supposed to be looking at/for.

However, I also kind of doubt that 9 women and a guy are all going to get naked and all do each other; there will probably be "pairs" or each person will have to do 2-3 others or something; it would be too long/complicated a lesson to have everyone doing everyone else and it could be the guy will be treated differently or will have other partners than your girlfriend, etc.