Annoying A** Kids...

So I have not been liking humans during most of my pregnancy but lately (for the two past months), I have been babysitting my little sister. She is 9 years old and I am 22... I decided to help my mother out bc she was struggling with after school care and finding a new home (all while working several double shifts per week). Anywho, my little sister has been annoying me severely. My husband tries to help me by telling me to relax and helping me out around the house BUT he isn't always there when she is (as he also works at night). 
It seems like everything she does annoys me... the way she chews, the way she kicks my bed when she's sitting on the ottoman before my bed and watching TV, and when she moves around a lot when I tell her to go to sleep... She also has the tendency to look back at me every ten seconds when we are watching tv or when she is watching and I am on my phone... OH AND the most annoying thing is when I wake up and see tissue all over the floor and in her bed... it drives me nuts... she rips paper tissue up and uses it for her nose at night because it becomes stuffy and in the morning (even when I tell her to make sure it's all gone), she has it on the floor, in the bed and in the damn hallway...
It drives me crazy... I think I get so annoyed bc of my pregnancy bc she was always annoying to me but now, it's really bad. I wonder if I am the only one who feels this way towards other ppl's kids? Please share so I won't feel so bad about ranting about a little annoying kid... LoL (I don't really feel bad, just curious).