Welcome to JustAnswer! I am a licensed veterinarian and would be glad to help!
How much does she weigh?
This is a reasonable dose, but one that does not have a strict need for weaning.
This drug is a weak opioid as well as having a small degree of with anti-depressant properties.
In pets it is reported to have very little addictive qualities.
If you want to be extra careful, you can go down to once per day for 7 days, then every other day for 7 days - but that would be extra careful.
Please help me understand her behavior after not giving usual dose yesterday--She exhibited signs of withdrawal (from what I am reading online) or is she still experiencing pain from surgery?
It may be pain from surgery, but one missed dose should not cause withdrawl signs.
How long can she experience pain from the surgery?
It should be gone in 2-3 weeks.