Do you see your mother in law like your own mom??

This is half a pregnant topic and half is not.

I have been married for 10 months, I came into an American family ( I'm Mexican) since the beginning of my married my mother in law told me that she wants that I call her mom, she has another daughter in law that is in the family for 10 years, since she doesn't call her mom she wants that I call her mom, but I can't!! I told my husband that I can't and he said that I should try, but I don't like the idea. Also now that I am pregnant she's been kinda annoying, we wanted to keep the baby sex as a secret, but all the time she keeps saying that she knows that is girl, then she changed for a boy... I'm so annoyed by that. I just can't handle her, she tries to be nice.... but I just think that I don't like my mother in law and I feel like a need to pretend I like her. I have been trying to have a good relationship with her to see if I am the one with the problem, but she doesn't let do anything in the house, when we go to visit I want to help and she doesn't like my help, she doesn't talk with me, only with the other daughter in law, she says that she doesn't understand my English... everyone understand me except for her. Now, when my baby is here she wants to move to our house and help me, I don't know how to say no to that.

Anyone have o had experience like this??