"I don't owe you ANYTHING!" "You're NOT entitled to an inheritance"

I'll try and make this as short and concise as possible. First off, I'm an "only child." - However, I have a "cousin" (my parents' niece) who they have basically raised on and off throughout her life. (She is a bit younger than me. (I'm 50s - she's 40s). Anyway, I've resolved in my own head to accept the fact that I am indeed "NOT" an only child - and that is right down to the "will / estate" - my father wants things "50/50" between us. I have accepted that. However, my father passed away a few years ago and my mother is still alive (late 70s). When my father passed we set up a trust of which my mother is trustee (until she's physically capacitated) and when she passes "I" am the trustee. My "sister" has NEVER liked this - (why? because SHE wants control).

Anyway - in the trust it is spelled out everything is 50/50 between us. Now enter into the fact that there is quite a large estate here (about $1 million) and my mother likes to play the game of "I don't owe YOU anything! It's not written ANYWHERE that parents have to leave their children an inheritance! ALL the Hollywood stars make it known they don't leave things to their children..." - Stuff like that.

This bothers me immensely - especially because my "sister" tends to (in my opinion) get into my mother's head about "me" .... simply because I believe it bothers her (my sister) that we are not "co-trustees" when my mother passes. I truly believe it is my "sisters" intention to continue "poisioning" me into my mothers head so my mother leaves EVERYTHING to HER.

Regarding "co-trustees" my adage is - you cannot have "two cooks in the kitchen" - we would NEVER agree about things (i.e., when to sell the house, what price to sell the house, how / when to distribute money etc ...) So I feel that on an ongoing basis my "sister" is constantly trying to plant ideas into my mother's head about "why" I should not be in charge - or at least we should be "co-trustees." Which leads to arguments between myself and my mother and my mother will come out with those hurtful sayings.

I realize that parents do not "owe" their children anything - but I'm being realistic on a humane level. It has always been MY intention to leave whatever I have to both of them - period. It's always been said by my father that he wants things split between me and "my sister." - And now my "sister" is saying things like "Well it's HER money now and SHE can do WHATEVER she wants with it. She can leave it all to charity if she wants!"

Anyway - just wanted to get things off my chest about how I'm feeling. Do you think by my mother having this kind of "attitude" makes me want to be around her? Am I wrong in feeling upset about all this? Thanks for listening.