Very nice little mare you have on your hands. Others have already pointed out what I would say on your position so I won't comment.
I would like to see her a little looser, I like to have my babies nice and big, loose and swinging more than up with the poll at the highest point. She looks far more relaxed in the photo's where head neck is being carried lower.
At this stage, all you want if for her to go, stop and turn more than look pretty. Have her react immediately off your aids and then work from there. Some trot-canter-trot transitions will really help you to warm up her back and get her loose, but because she's only young don't over do it.
Lots of changes of rein and transitions will get her nice and loose. The biggest thing is to have her relaxed through her back to help her build up those muscles. It will take a while for her back to develop enough to get true swing and throughness, but to develop that you want to get her working actively behind and light in the bridle.
Good luck with her, she's a very flashy little mare!