Am I a bad mom?(reposted because I wanna hear more opinions 😳😳)

So my little girl is 3 and boy is she feisty. She hits me and her 8month old sister, yells at me, smears poo still, she hardly ever listens , glares at me and gives me dirty looks, and takes without asking as soon as I turn my head. (Ex: I said don't touch the banana on the counter , it's beside a very sharp knife , mommy will get some for you in a second, and I turned my back to put something away in the fridge, and I turn around to find her grabbing the banana THAT WAS TUCKED UP BESIDE THE KNIFE)I scolded her and sent her on time out, but it's like that every day. My parents live 1800 km away and have offered to come get her and give me a break for a month(I just got her back from them on July 1st..after her visiting for 2 months) but seriously , I'm not doing this for ME. I'm doing this for her. My hormones are terrible. I'm always snapping at her, I'm never happy , not hyper , just exhausted and sick.. (Bronchopneumonia) And I'm a little uptight at the moment. My parents ? The complete opposite! They're upbeat and always happy with her, punish her nicely when needed,and she loves their animals.she always wants to call them too. My mom agreed to come get her this Tuesday, I agreed.my in laws never help& they never care(literally even if I'm bleeding or need to go to er & I'm expecting)& my fiancé works out of town. He's agreed it sounds like a good plan, but I feel so bad. Am I selfish ?:/
UPDATE:
I'm not treating this as a punishment. She is asking to go and insisting she goes and asking how many more days and when her grandma is gonna be here , SHES EXCITED. She is going for just a month & im not "sending her off" jeez. Make it sound like boot camp.
Update again; I do spank and she ignores them! Even tried them bare bum but nothing works :(
Update AGAIN;
I tell her to go to her room when it's nessecary, and she tells me no. Over and over and I used to have to chase her to her room.. Now I take her arm and pull her there... And she pulls the other way HARD. I give her two warnings& then tell her to stand up for a spanking.. Today she yelled no  at me and threw herself and started thrashing while I was pulling down her pants to soank her bum. After that she screamed and kicked so I took away her blanket & pillow (time out is sitting in bed) & that made matters worse!! So my fiancé went & attempted to control her off and on for an hour before she finally passed out..