I feel like a bad mom

Do you ever just feel like a bad mom? I know it’s a dumb question, but today I just felt it a little extra.This is going to be a bit of a rant/advice ig?

She threw a HORRIBLE tantrum , (screeching at the top of her lungs, sobbing uncontrollably), over me sitting in a chair she wanted to sit on apparently. That’s when I knew it was time to go to bed which made it 10000x worse to even mention bed time. Now, she has gotten this bad habit from school (I’m guessing) where she says “I don’t want you anymore” or “I don’t want my family” and I immediately tell her that’s wrong and that’s not ok. I put her in time out, because afterwords she ended up smacking my husband and she immediately always says I’m sorry so she can get out of it and when I tell her she still needs to stay in time out, more screaming continues. Once time out was done (she cooled off) I explained to her what she did was wrong and it makes mom and dad sad when she acts like that. We told her we loved her and we don’t like yelling at her but how she was acting was not ok. She seemed to understand and apologized then we put her to sleep. I just question myself like, am I doing something wrong? Why is she acting like a brat? Am I enabling this bad behavior somehow? I’m an over-thinker and have anxiety so I’m constantly worried about being a good mom or teaching her the right things. Sorry for rambling on, I just needed to get this off my chest.