Yeh does look like slipped tendon, if you take the leg put it towards the back of her, and pull just a tab, you should feel a popping, if it pops then it's back in place but here's the tricky part, you have to split it so that it stays there until the tendon heals back that is IF the tendons heal. I have a duck that has slipped tendon, and now I have a little baby chick with the same issue. When the ti swells like that, it's really hard to recover from unless they have surgery done. Lots of vegetables and vitamins is what they need to help the recovery. it's going to take a long long time that is if she does or can recover..