#1 - She looks a little scared, and I find the crop & framing a little strange.
#2 - Expression & pose seem OK, perhaps the angle is a little distracting.
I like #3 & #4
#5 Looks like a bit of a mug shot, stand here, shoot.
#6 The frames hide the eyes a bit much for my liking, I'm not someone who thinks girls with glasses aren't pretty (both of your models are very pretty), it's just that narrow frames can be hard to get on an angle that doesn't block the eyes, maybe have her remove the glasses next time.
I think the model from 5 & 6 would benefit from a different angle too. (Like 3&4, but of course there are so many three quarter poses). Look in books or magazines for shots you like and try to replicate the poses. The more you take, the more you'll start to recognise what will work before you release the shutter.