I'm going to cut contact with a cousin
Why are you gonna cut contact with her?
She complained too much when she visited me
I know you're upset but it's expected to stay connected with family members. You should try and come to an understanding with her.
Nah, she was annoying and it's my choice since she's only my cousin. I think she complained about everything in sight including the food I made for everyone. She was the only one who hated everything.
There are people who love to complain for the sake of complaining, they will never change. Take some time for explaining to her that things are not going to go entirely her way at all times.  Just stay in touch regardless of her bad attitude, she could change one day.