Mean toddler, your thoughts.?

My neighbor has a 3 year old lil girl.Shes about to be 4 this summer.My sons 2years and 6mths old.Her little girl is a brat.She kept taking my sons toys,his sippy cups,taking his toys out of our house and taking them to her house.Her grandmother had given them back to us when she found them and knew they werent hers.At his 2nd bday party she tryed to rip every gift he had open,he got an elmo plan and she kept running it hard into the walls and our front door.We live in a little mobile home park and they are the only lil kids here.We are the only ones with out side toys like a swing set and a little house play thing and a wagon and a really nice power wheels car we just bought him.And I know shes little but keeps saying that all of my sons toys are hers and her mom doesnt really get onto her being mean most the time she just yells at her.So I cut ties off a few months ago bc she started to hit my son and her mom wouldnt do anything bout it really.And they other day her cousins came to vist there grandparents who live infront of them and he was playing w her cousins, she comes along and kicks the kids out of my son little car and starts driving it into trees and crap.So her mom got mad bc her grandpa told her to get out and she cant play with it again bc she was messing it up.Theres no way i would let my son mess other kids toys up or even let him take things from other kids.I mean the little girl has toys,and tells every one she messes other kids toys up bc she doesnt have what they have or she wants it.What would you do if this was you child doing this or this was happening to your child.Like I said I cut ties off with her and her mother months ago bc I was tired of how my kid was being treated and I was always being used....do u have er do u have surgar or can u watch my little girl for a little bit. Acted like my friend but really wasnt.