My question is just how many times do we forgive them for unacceptable behaviour?

Demonstrating we won't accept their bad behaviour is liberating. My mindset has changed and I no longer feel downtrodden. Think this annoys my mother even more. I will not allow her to destroy me just because her own mother behaved that way.

The main problem has been her inability to treat my brother and me equally. Openly displaying that he's her favourite, including making comments to anyone that listens that I'm a bad daughter, etc. Only recently have I been able to rectify this situation with my aunt. Her comment, "now I realise it's not all you".

You are you and not someone who is manipulated into being a replica of your mother, unless you really want to be. Despite what they may say, our mothers are not always right!