When my vet suggested reducing Karla's meds he suggested I cut the tablets into quarters and give 3/4 instead of a whole one, then later go to 1/2 but keep giving the tabs twice daily so she didn't go too long without pain relief. Luckily for her she rarely need them now.
Phone your vet and ask what way is it best to reduce the tablets for Misty, it may be a case of just tweaking the dosage to get it right for her. ..give her a gentle hug from me. Sorry I couldn't be more help.