U can get the spaying done for the pet
Before the surgery u have get a blood test done
If the parameters are normal surgeons will place the surgery on particular day
So 12 hrs fasting should be done before the day of surgery
OHE can be done, but you should make sure there is a gap of at least around a month from the previous heat/ estrus period. Get a physical examination, blood test and an ECG done to see if your pet is healthy for the surgery before you take an appointment. Post surgery recovery time is usually a week to 10 days. Make sure you are relatively free around that time to attend to her needs during that period. Post operative care like antibiotics and maintaining e collar would be very important for smooth recovery