My big girl is 4.5 and the baby is 10 months. He has just turned into a little crawling and cruising machine, which is great...but DD can be so mean and controlling with him!

It is driving me crazy and I need help to figure out how to address it: for example we have a little walker. DS will push it, then get distracted and transfer to the ottoman for a minute before going back. But in the brief time he is away, DD will swoop in and take it. Then DS cries. She likes to make him chase her except she won't ever let him catch her. Also he doesn't really know how to chase because he is so little.

How would you handle this? Will I drive myself crazy if I try to keep addressing this?