My oldest DD is 6 and in Kindergarten.
I completely understand where you are coming from! Here's some random thoughts from me! :D
What does she usually do between 4:30 and dinner time @ 5:30? Maybe you can limit it to just that time of day while you are getting dinner ready.
She's probably lonely ...and that's prob not helping you feel better! LOL Sorry! But regardless, her Mom needs to take control and realize that other families/children can't always play all the time. That children need to spend time with their families...and why isn't