My sister watches porn, and she is only 12. She does it to learn since my parents don't wanna teach us. Is that okay?

No it is not okay because porn teaches lust not love. There is a world of differencebetween porn sex and love sex. In fact true lovers don't have sex, they make love to each other instead. But I believe it is a parents duty to teach the facts of life. There are the biological facts (that porn does not teach) and the emotional facts that are very important.. Can you ask another adult in the family to talk about any concerns that you have. If not there will be websites for youngsters to teach them the birds and bees.

She doe it to learn? That's the worst excuse I've heard of. She likes it, that's all there is to it. She is way to young to be watching that stuff. Your parents should know what she is doing.
Parents do not teach sex. They tell you about it and the rest is for you to discover.

As a parent myself  I think 12 is a little too young to be watching porn. I think she would have trouble figuring out what is real love from the fake. Get her to wait a few more years.

That's not okay. She's only 12, I can see why your parents don't want to teach her right now. She's still too young to be learning such things.