Need help with adopted toddler

So, my family adopted two toddlers. A random boy from the game, and a girl that was previously neglected in another family I built.

Now, I'm having some trouble with the girl. She refuses to learn to walk, talk and go on the potty. I've tried multiple times a day during her time as a toddler and she throws a fit every time. Her stats are good and she has a good relationship with her parents so that can't be the issue. The boy doesn't have these difficulties.

Has anyone else experienced this? Could this be because of the previous neglect she encountered?