She's just not herself - is this to be expected?

Roxy was speyed on Friday. The op went ok as far as I know, the vets kept her in for the day, made sure she ate something etc.
She came home Friday evening and she was soo hungry, she ate a whole pouch of the food which the vets sent home for her. She started to bite her stitches so I had to put an Elizabethan collar on her, which she hated, but she got used to it. I took it off on saturday morning and she mostly left her stitches alone. She's now bitten out the outer stitches but the inner stitches are clearly still in and the wound looks fine.
She has been quite normal, racing around, then a bit sleepy, maybe a little less energy than usual. She's been quite fussy with her food, but eating little bits of food, sometimes stealing our other cat's food.
But then yesterday evening she was sick twice and just looked really fed up.
She's still playing a little bit this morning and has eaten some food, but she's just looking fed up. She's going to the vets for a check up tomorrow, but should I take her in sooner? I'll probably call them for advice too.
I'm not surprised she's fed up, she's had major surgery so she's probably feeling pretty rubbish, but I'm so worried about her
:-(

I think since your next appointment is soon, that should be fine, but keep a close eye on how much she's eating.