Yep, I read that article too in the newspaper that Mallory P. mentioned.
There is a wide age difference.
The older one is doing this on purpose. Thus you gotta nip it in the bud.
A 2 year old, is not cognitively developed enough to self-manage her.
You sit her down. Explicitly state that her behavior is unacceptable. And then do what Mallory P. mentions per the article.
You ALSO, need to explain to her, what a sibling is, what a family is, and that you ALL are a "TEAM". And that as a family, you look out for each other etc.
My daughter was 3 turning 4 when I had my 2nd child.
I explained to her, what a baby is. And each month, I explained to her, how her little brother is doing, how he is developing, what he can or cannot do yet because he is little, and how SHE was like that too. He cannot do what she does. SO... we all have to understand. He is little. He doesn't know things like she does.
My daughter, thus, responded well to her little brother... and developed "empathy" for him. And she would actually look out for him and help him. She would tell me "M., brother is in his tantrum phase....." etc. And she'd KNOW what was going on. Or she'd tell me "M., he's yelling because he can't talk yet...." etc.
So, she learned about her little brother, because I explained to her about his development monthly, and she understood. Instead of antagonizing him or misinterpreting him.
My daughter, understood these things even at 3-4 years old.
Your daughter is 5. You can certainly explain these concepts to her and she can understand.
My daughter and her brother are very close.
Explaining to the Eldest child, is necessary. Otherwise, they do not know, anything, about their little sibling or how they are developing or not.
Versus, them.
But yes, you teach your daughter, about HOW to be a sibling, too.
It is a learning curve.
For outright mean-ness to her sibling, you need to correct her. And be consistent.
It is not right.
My daughter was an only child, for 4 years.
She adapted well to her little brother.
Because I explained everything to her, even while I was pregnant with her little brother.
It 'prepped' her... for what a sibling is, and what a little brother is.
all the best,
Susan