Sorry...didn't know you were asking me the questions about subq and appy stimulant.
If she is still showing ketones or is dehydrated, then ask your vet if she will give subqs again. To check for dehydration, lift up her scruff and let it go. It should snap right back into place. If it does so but slowly, she's dehydrated. The other way to tell is to rub your fingers over her gums...if possible. If they are tacky and not slick, she's dehydrated.
Insofar as the appy stimulant, you want to be sure she is not nauseous before you give an appy stimulant. If she sniffs her food and walks away, drools, sits hunched over, she's likely nauseous and needs ondansetron (zofran) 1 mg bid (the tablets are 4 mg and you would give 1/4 of a tab bid). The vet might want to give cerenia. that is usually for vomiting. I'd also try for cyproheptadine as an appy stimulant over mirtazapine. Either might make her agitated and cry. Using them for appetite stimulants is off label.
Let's just hope she eats in the morning.