Help my child is very angry!!

I have a 20 month old and she is very out of character. Pulling her hair, biting her hands. Screaming non stop this afternoon!! My sisters came round to see us all and she was fine. Now she's been very nasty and slapping, bitting. She's always in a good mood usually but the hair pulling isn't a shock, she does it when we say no or when she gets angry. I feel like I've failed her after seeing her get like this. She has proper tantrums and it's soo sad to see this 😰 what can I do to help this? I don't always stay calm I'm not going to lie. Sometimes I do raise my Voice so I'm probably half the reason she's got like

This. I have a two month old baby and since his been home she's been quite out of character. She's never hurt him, she always kisses him and is gentle. I don't know what else I'm doing wrong. Is this even normal? I want to stop this before more damage is done.