Andromeda I think is a hard working, determinded woman while Narcissa I think is clever but not so hard working. Bellatrix is just nutter and would probably only be interested in exams if they had one of the Unforgivable Curses in them.

Definitely

I think all three of them were good students but I'd assume Bellatrix got herself into trouble and Narcissa was busy with MakeUp

Def she kept herself to herself wasn't interested in things around her, or the death eaters.