I had to make that decision myself...
My two furkids who I grew up with both live with my Mum. Both were very close to me, Whiskey in particular. When I moved interstate, she was quite sad, but I was moving to an apartment which did not allow pets, so she could not come. It was agreed that Mum would look after the cats.
When I moved into a place where I was allowed one cat, Mum hinted heavily at me taking Whiskey to Brisbane. I agreed, although I was a bit worried about moving her after she had had lots of unsettling moves already, and was just beginning to calm down. I was looking forward to seeing her, as she is a VERY cute little girl.
In the end, however, Mum backed out as she was too attached to Whiskey and I got my Pixie darlin'!
Whiskey is still my special girl and still remembers me, however, she is happier with Mum as she is settled and knows the place well. Perhaps it may be the same with your special girl, or maybe she will be better off with her special human. It is a decision you need to make, bearing in mind that your parents may also be too attached to let her go.
Personally, I'd leave her with your folks and rescue more kitties in need as the four with your parents are already in a great home!!! :D:D:D