Anyway I did a redline, but looked awkward ontop of the image and hard to make out so I moved it beside. Ignore my bad writing it says
3 joints, shoulder, elbow and wrist in the front leg. Back rounds out slightly, when sitting a dogs back is will be mostly straight or slightly rounded out. The back leg when sitting doesn't attach to the rear end, it overlaps on the dogs leg. Hard to explain I am going to post photo references. The back legs are also determined by the way the dog sits.
1 2 3 4 5 There are a ton more but good start.
The best way to improve is references and real life study.I suggest looking up dogs sitting in different angles and poses and drawing them, this will make you comfortable with the way their bodies are when sitting.
EDIT:
@Solloby: You are right when thinking the front legs are too long. They are out of proportion to the rest of her body and back legs. Her body also looks like you are turning it slightly, since you can see the front of her chest and paws. I would recommend turning her face out of pure profile into a slight 3/4. The back leg knee should be lower, here is an example of it in a dog cause my explinations aren't very good Click. I went with a dog, assumed the anatomy was closer to a canine, but if not sorry.
I would redline but I am worried I would change it too much.
