When my grandma gets mad at me she says that she regrets adopted me

Hey everyone, hope you are great, I am 20f I was adopted right when I was born by a woman (my mom who I love so much) and we have always lived with my grandma (my mom's mom) who I also love but my relation has never been so good as it is with my mom.

Since some years ago, my grandma has started to being absolutely mean, she says that my mom has miseducated me and keep saying her things like: When she finishes college she is gonna be independient and you are gonna end up alone because I will die, so it is useless that you defend her.

She says that my mom defends me when we argue but she has spent her whole life saying so hurtful things,

I remember when I was 8 she told me: You are so dumb that you will even alow the dumbest man in the earth fuck you. That marked me a lot honestly I still remember.

Today we argued and I confronted her because of the mean things that she says to my mom and she said: everything was fine until you arrived, so I replied: then why did you adopt me? she replied: I still regret it.

I feel so bad honestly, I feel so grateful for all the things they have given me, the love my mom has given me, the education, shelter...but I cannot fake that this does not affect this kind of things makes me have moments of rethink about everything.

Honestly I just needed to vent.