Its comic relief and something I like in anime.I used to watch a show called Justirisers,a Japanese Power Rangers rip off and the female lead also hit the main similarly which isnt there in the American original.That's his mother. Your best friends would not hit you that way.
Doesn't matter though. The only thing I like about Sakura is her relationship with Naruto. Really close bond they have, seriously. It's honestly Sasuke that ruins her character.
imo
Then kids shows like shin chan also have the mom literally hitting her son 5-6 tims each shows