It's years ... far too many since I did any of this....
As stated Depth of Field issues, I'd not use any less than f5.6, might mean moving further away from back ground... so be it.
No.2 Eye keeps getting drawn to the black strap on the right, very distracting, re-crop, or clone it out !!!......(or ask her to take it off next time !
No.3 There are no rules in Photography that can't be broken, but I was always told your eye line should always be higher than hers... Never look up to a girl !!! (Insert own witty comments at leisure !!) it's not faltering to them...double chin effect.... Compare 1 and 3 you can see the effect.
Also get any old flash gun and put it on the floor behind the model, experiment with firing at the back of her head, or on the wall behind for a back-light effect...