wow! I think you managed to extract the hair very well! (it's always a difficult matter)
and the idea of the background with the reflection is really excellent
there's only a small detail where my eyes go which ruins a little the overall composition: I feel that the reflection under her foot should be a little bit darker, just to show some shadow so that she really looks is sitting there.
she's so cute! she will be a wonderful model for you..... i'm really sorry for her dog, she must feel very bad..
as for the hair what I do is to use the selection tool with a higher feather and then use the smudge tool to create some "loose" hair and, if necessary, draw new hair with a tiny soft brush