Is it normal to feel irritated by your child/ren?

Lately my daughter has been really irritating me. She's 7, and she thinks she knows everything and it gets on my wick. She also interrupts whenever me and her dad are talking and she's started being really defiant about stupid things (like if I say wear underpants then she'll say no etc etc). Don't get me wrong, I love her to bits.......but she's irritating me. It grates on me a lot I think because when I was little if I did half of the things she does now I would have got a wallop. I don't agree with that, and I give her respect and value her opinions, but it just seems to make her really big for her boots. Is it normal to feel irritated by your child?