Please remember your cat has had major surgery.
It is normal for pets after a general anaesthetic to not eat within the first 24 hours after surgery, if she is requiring a little extra fuss attention during her recovery with regards to eating and drinking this is normal for first few days.
it is important you restrict her exercise over the next 7 days especially to allow things to begin to heal ie if she is an outdoor cat, keep her indoors etc, the collar is there to prevent her interfering with her wound, these are better tolerated by some animals than others, it is only temporary and your cat will soon be collar free!
Just check the wound by looking only, daily, is there redness or swelling? any excessive discharge? If covered by a dressing is this coming through? If so contact your cats surgery but do not bathe or try to clean the wound.
You should begin to notice an improvement in your cats demeanour gradually over the next couple of days.
Just remeber once all this is over your cat will be much happier in general and you have prevented many associated health risks.
Best wishes to yourself and kitten.