Aggressive towards kittens after spay??? HELP!

Hello,
I just got mom and 3 babies spayed yesterday, and today mom is acting very aggressive towards her babies - not so aggressive that I couldn't keep her in the same room with them overnight, but aggressive enough that I wouldn't do it again. (12 week old kittens)
I've never had this happen with a cat after a spay. I wonder if this will pass or what's going on?? One in particular always tries to nurse when she comes around - but hasn't tried since she got spayed. If they even get close to mom, she swipes and hisses and growls.
Any help?

some cats react differently, sometimes its the smell from the vets, or she might be having some pain and maybe a bit tender.

thank you! I actually took my little Tattletale to the vet and she said that it's probably from the pain and the cut in hormones.

did they give her some pain meds? some cats need that litter bit extra, sometimes they will give you some to take home with you.

They didn't. I got her done at a low cost spay clinic so I didn't get anything to take home. She seems a little bit better this afternoon - she still looks a tad bit groggy, but so does my other gray girl that looks just like mom. Probably just the pain.

aww im glad things seem to be calming down a bit.

I wouldn't want my kids pestering me after a major surgery either!!! She will feel better in a few days.