I can relate to your situation. I have been questioned by both my mother and mother-in-law. Mostly, it comes down to boundries and respect (or a lack thereof). One example, in particular, comes to mind.
I was in Florida with my two daughters (at the time one was almost 5, the other was almost 2). I was seven months pregnant. My sister and her fiance and my mother were also there. In our first two outings to the pool, my oldest daughter (who is very strong willed) showed absolutely outrageous behavior. To make a long story short, I started out trying to be very understanding and patient but when she started to run away when we were leaving the pool, I knew I had to be more firm. (I just couldn't chase her and her sister with my big ol' pregnant belly in 90 degree heat!) I told her if she didn't come with us to the car right away, she wouldn't be able to go with her g'ma and aunt to a Disney thing that night. Well, she didn't come and I had to carry her, kicking and screaming, to the car and then she screamed all the way back to the condo. When it was time to leave for the Disney event, I wouldn't let her go. My sister and mom thought I was being way too severe but I knew I couldn't back down or the entire trip would've been spent fighting my daughter. My daughter cried herself to sleep that night, and I felt awful, but you know what? The rest of the trip was awesome. She listened the first time I said something nearly all of the time. And we all had a blast the day we went to the Magic Kingdom (something I was dreading). My mom wouldn't admit that I was right, but she was impressed by the change in my daughter's behavior.
We also have trouble with the other g'ma and overnights. My daughter comes home high-strung and sassy every time. I sort of put up with it when she was younger, but now I have two other girls and just don't have the patience for it. One day I actually called my mother-in-law in tears and said, as gently as I could, that I really needed her to listen to us more about bedtime, too much soda, and letting her always get her way. Things have gotten much better since but she tells everyone repeatedly that grandmas are for spoiling and I don't think she believes how naughty our daughter is after one of her g'ma visits.
Well, sorry for the long response. In a nutshell, you and your husband know your daughter best and you have the responsibility of raising a kind and respectful woman. I think extended family is VERY important, but I'm all for extreme measures if sincere communication isn't working. It sounds like you and your husband are on the same page, which is very important, and also like you're actually trying to do some teaching about behaviors and consequences. Best of luck!
R.