As no one else has had a go I will. Hope it helps.
Overall it's not good, firstly it's not flattering to the model with her head (the point of interest in my opinion if I'm shooting people) is stuck way up at the top of the shot and we are left with a load of dress and wall to look at. Try getting more level with your subject in this case.
The single arm is bad because having to support herself her arm is tensing and looking bigger than it should, the other arm should have been straight down so we can see it's there.
A better pose would have been sat on the step, then work on some variations of the rule of thirds as you look through the viewfinder, inc some head shots and wider shots, if you do some more model shoots try taking a few 'tear sheets' from magazines of pose's you like and concentrate on trying to acheive the shot.
Don't be afraid to move around your subject while shooting, don't stay on the same spot, do keep reviewing your shots as you go along, inc the histogram, this only takes seconds and will result in better work.
Hope my crit hasn't put you off shooting models