New Here (its gonna be long)

I have never posted here before, I actually havent posted anything in a long time.

A little background: My DH and I have been together just under 8 years married almost 2 years. I have 4 kids myself, they live with their dad, by their choice not mine. My DH up until about 3 weeks had no kids. We just found out and had a DNA test done on a 12 year old girl. It, obviously was positive. Now, ive had stepkids before, not a big deal to me. It gives me another child to love and Ive promised I would treat her no different than my own kids. Now, onto the problem, Her mom is in the Army and SD lives with her grandparents until BM gets settled. Well, SD seems to think that now she knows her dad, she can run him over. EX: We were with her the other night and she told him 4 times to shut up and he didnt say anything to her. He later told me he didnt hear her when I mentioned it The night they told her he was her dad she immediately made a list of things she wanted DH to buy her. I totally understand making up for lost time, but I down right refuse to let him buy her love. As far the grandparents go, the GP is awesome, the GM not so much. She is totally drama filled and controlling. She made the statement to me that they keep SD occupied a lot so DH may not get to see her much. I have to give him credit, he stepped right up and didnt think twice about it, weve been to see her twice in the last week(about 45 minute drive one way) and we spent all day last Sunday with her.

I guess what Im doing is more of a vent than anything, but if anyone has any advice on how to deal with the GM and the controlling Id appreciate it. Im sure I left a good bit out, but any questions you may have Ill answer as soon as I can

TIA for any help!