Do kind people have a “mean” side sometimes?

One of my aunts (let’s call her Aunt Bea) is a kind hearted woman but she can have a very feisty side at times. When one of my other aunts (let’s call her Aunt CeCe) called Aunt Bea and my cousin (her day cousin), we said hey to her.
My aunt Bea was like, “I don’t wanna talk to you!”
CeCe: Oh what’s the matter? Sissy forgot to take her pills this morning lol. Can’t I talk to my own sister?
Aunt Bea: Oh shit up you old heifer! You don’t even call me much so why would I wanna talk you, bitch?”
Wow!! Really Aunt Bea?! That was so rude!!!! How can a good hearted person say such nasty and have such a “mean stream?” 😳😳😳😳😳😳
Aunt CeCe laughed and Aunt Bea laughed too. They talked. Wow Aunt Bea could have been a bit nicer. I whispered to my cousin that her mom was rude and she laughed and said, “Oh Layla. They’re sisters. They poke fun at teach other all the time. Siblings aren’t nice to each other all the time. You should know that. Plus that’s how they bond.”
How can some people bond by insulting each other jokingly? That’s SO RUDE!!! 😩😩😩😫😫😳😳😳😳😳