I had this exact situation too!! Mom and dcg brought in an item that she never played with and mom was going to sell in their yard sale but she brought it here first and asked if dc would like it. I said, sure.

The kids loved it (drs trolley) and they all played with it all day.

Fast forward to pick up time with dad. She was last child here and threw a FIT!!! She refused to come up the stairs where we were already. She was crying, whining, wailing that she wanted her toy back. I will say that at first dad did well and said no they didn't need it, she could play with it here, it was a gift blah blah blah but he eventually caved when she started to drag it up the stairs herself. I was so shocked at how it went that I was speechless lol. I talked to her the next day about it and said that her home toys were not allowed to come to dc again.