I feel so bad for my best friend and there is nothing I can do about it. 

If she is ever sad, she gets yelled at. 

If she cries, she gets yelled at. 

If she says, "no" she gets yelled at. 

If someone is mean to her, she gets yelled at. 

If she doesn't want to clean her house and scrub the floors because she has homework, she gets yelled at. 

If she wants to skip her church meetings to hang out with us, she gets yelled at. 

She isn't allowed to see me anymore. Friday's she has to go straight home to go to her church where she isn't allowed to talk. 

Saturday's and Sunday's she has her church confrences all day. 

She isn't allowed to listen to mainstream music, she isn't alliowed to watch new movies, all she does is sit around and watch old movies (Shakespeare; I know) and crouchet. Which is pretty entertaining, but she has no internet, no junk food, and she is always really sad. 

When she didn't want to do something, she got yelled at by her mom and blamed it on me, which I think is crazy.

One time I went to dinner at their house and my friend said something that made her whole family laugh at her, so I said, "It's ok, I agree with you," and they all kinda stared at me, for defending her. 

I honestly don't know what I do wrong. I have good grades, I'm nice to everyone, I don't do drugs or drink or anything, I don't have a boyfriend, the only difference is that my mom gives me so much more freedom than her. I am always having her (my friend) over for dinner and we drop her off after school. We're so nice to her I can't believe her mom is doing this to us. 

I know she loves her mom and there is so much going on in their lives, but my friend is getting depressed from being yelled at and not being able to do anything. Her mom says she is snobby when she hangs out with me. My friend sent me a whole long text and she is crying now. I love my friend I can't just be like, "Ok, whatever bye," cuz she is my best friend and I can't just ditch her. I can't believe this is happening to her. 

Please witty; what do I do??

I'm not asking for attention  or faves. I just need advice.

Please, anyone. How do I help her when I'm never allowed to see her again?