I kinda like this picture BUT it is a little difficult to tell what your subject is: it could be the hand touching the violin, because its in focus, but then its right in the middle of the frame and its very small compared to your sister. Your sister also pretends to be the subject as she is well positioned according to the 9-zone grid, and she takes up 1/2 the frame but she isnt in focus and her right hand is cropped out.
I would say if you wanted to focus attention on the hand touching the strings on the violin, you shouldve blurred the background more, maybe underexposed by 1/3 a stop and changed the angle so that less of your sister would get to be a part of the picture and the background would just look like a bunch of abstract shapes.