I really like the colors and the expression in this piece! However, the willows are a bit off. They look more like stacks of hay. Try taking reference pictures next time! Then you'll see that it's actually the branches hanging down with leaves on them. Now it looks more like the leaves are thin and long, if you get what I mean.
I get a very lonely yet peaceful tone when looking at this composition. I think the girl sitting by the lake was cleverly placed, with the soft greenery of the willow trees surrounding her...Beautifully done!