I agree with Don about the posing. Also her expression seems a bit uneasy. Learning how to pose and also get the subject to relax is something I have struggled with too so I can’t advice much sorry! But I think these are areas that you especially need to focus on. There have already been good links posted. Another thing is I would suggest is watch your backgrounds as the woodland is a nice setting but in a couple the branches cut right through your subject, such as here
You have a pretty model and the images are well executed so with some reading up and practice on posing and eliciting good expressions, you will have stronger portraits.