Horrible Person

I hate it when I am a horrible person and do spiteful, vengeful things to people.   My mother and I had a huge falling out several years ago.  She insulted my family and moved out of my house.   But then she cried and said she couldn't go on if I didn't stay in touch with her.  So I call her three times a year and email her every single day of my life.  I emailed her every day before the fight, but I used to call her several times a month.   The phone calls are too painful for me so those had to go.  The emails are bad enough.
Her emails are full of how she doesn't like the town she lives in   How she never has any family for holidays...  All stuff that is her fault she announced she was moving out as she couldn't stand the way we lived.   All we did was try to be nice to her. 
So sometimes when I get those emails I snipe back at her.   Today she wanted to know what time would we be home so she could call and wish my husband happy birthday.   Well she has not called anyone at my house on their birthday in years.   She called maybe the first year after the fight, but then stopped.   She doesn't even always send gifts on birthdays.  She sent me one this year, but not last year  And this year she didn't send my husband anything.
So I replied with times she could call.  Then went back and typed in that she was welcome to call, but had been years since she had done so.  It was mean and petty, but she rejected us, then demanded that I stay in touch.  Stuff like not calling my kids on their birthdays hurt me and probably hurt them too and sometimes I feel like hurting back.
My mom, the one I knew and loved and who loved me died with my dad.   This stranger I would like to cut out of my life and can't   I still hate it when I am mean when I don't have to be.  I am just not a nice person inside and don't always keep it locked up.