I have a very aggressive 6 year old daughter who regularly has violent outbursts, her sister is 8 and has always been very quiet, placid and sensible but she's also very sensitive.
Dd6 will throw things at her sister and call her names, hit her and bite her and can be really hateful towards her.
They share a bedroom so there's no escape for dd8 who is very tolerant but gets very upset and no matter how we try to deal with this nothing is successful, we've tried sticker charts and time out, taking things away, firm talking to but she doesn't change her behaviour and it's quite heartbreaking to see what her sister puts up with.
They do play together and most of the time they are fine but dd6 can change without warning especially if she's tired.
Dd8 never retaliates and forgives her every time.
I don't know how to handle this as it seems we've tried everything possible and get nowhere.
She's also like this to us but dd8 does seem to get the brunt of it.