Who is attacking you? The 7 year old?
That comes with the territory.
If her mom says no to something and you, from the way it sounds, agree with her mom, I don't think I understand the problem.
On the other hand, her mom might let her do things that you don't agree with letting her do and that's okay too.
My step son tried convincing me that his mom let him do this and that and you know what? It didn't matter to me. First of all, he was blowing smoke up my rear end and secondly, he wasn't at his mom's house when he was with us. I'm not talking about innocent things like staying up a little later on weekends. He spun some real tales about what his mother let him do.
Any kid worth their salt will try it. At least once or a few times.
And, if mom says no....a kid will ask dad in the hopes that he will say yes. If mom and dad say no....there's step mom to try it out on.
It doesn't sound like she's asked for anything too crazy and it sounds like you handled the situation appropriately.
The worst thing you can do is just give her what she wants, against your best judgement, so she'll "like" you.
If the girl thinks you're being mean for not letting her have what she wants....dang right. You're mean. The evil stepmother.
Don't get played like a fiddle.
You know what's right.
Best wishes.