10 yo stepdaughters behavior is a mystery to me

I honestly do not know where to begin... My 10yo step daughter is a wonderful sweet child, but I get the impression she has never been corrected and is extremely coddled at her mothers house. I understand protecting your child from the bad things in the world, but I am concerned that she is actually being harmed. Just as an example, I had to ask her to sit in her chair at dinner in a resturant this weekend, because she was climbing on the table. I also had to ask her to use a fork to eat fruit. We attended a family function at a relatives home and after about an hour, she quit playing with the other kids her age, found a TV and without anyone's permission, she watched TV for the rest of the day and did not interact with anyone. This morning, in another resturant, we had to tell her not use her hand to "lick a bowl of whipped cream clean". She cried when she was told this is not appropriate behavior. She is a smart child. She is a kind and sweet child. And I really want her to be the kind of person other people want to be around, but this is a little much!
She is only with my husband and I 2 weekends a month and it is very hard to really do anything to change the situation. I know it is different when she is with us than with her mom, but I really feel she acts more like a 7 yo than a 10 yo.
My husband says there is nothing we can do really because we aren't with her nearly as much as her mom, but I am honestly worried about what will happen when she goes to middle school and high school...
*note: She and her mother sleep in the same bed and are best friends. She only has 3 friends that she spends time with and they are all very much alike. She doesn't go outside because something bad might happen or someone may take her. She has absolutely no desire to have her own space.

[Kevin Kennedy, Ph.D.]

I understand your concern, but there really is little or nothing you can do if she spends so little time with you. If you and your husband are concerned about how she is being raised, perhaps you should be pursuing a change in the custody arrangement.