Hold on, Grl. I'm not saying what Xh is doing with kid is right, but I am challenging your belief that her developing a relationship with her aunt isn't valuable. Why is your family better for her that her dads family? If she was spending time with her dad would you use the word deprived? Why use it when she's with her aunt?
You may have explained some terrible character flaw in auntie earlier and if so I apologize. But it's coming across and you trying to control Xh.