Hello, My name isXXXXX and I have over 20 years of experience as a veterinarian.
I am sorry to hear that Holly tangled with a feral cat yesterday.
Tremors can be due to muscle weakness, fear, pain, fever, or electrolyte abnormalities in the blood as well as exposure to toxins.
Her encounter with the feral kitty may or may have something to do with the way that she is feeling today. It is possible that she sustained bite or scratch wounds that aren't apparent to you yet. It is common with cat bites or scratches that they are difficult to find and may only become apparent if they become infected and drain or abscess out later. She may not have a fever now but that doesn't mean that an infection isn't brewing.
Have you taken her temperature rectally? A normal dog temperature is 100F to 102F, a fever in a calm dog is a rectal temperature over 103F.
Of course the other concern is that she isn't current on her Rabies vaccine. It is much too early to show any symptoms of Rabies, that can take at least a week or so. If she isn't showing any symptoms in 10 days I highly recommend she be vaccinated as a preventative measure for the future. For now she should be confined closely to watch for symptoms including fever, lethargy, drooling, incoordination, possible seizures and a change in personality.
Ideally she should see a veterinarian and get started on some antibiotics.
If that isn't possible this holiday weekend then try to look for wounds and bathe and flush them with a solution of warm water and antibacterial handsoap a couple times daily.
To try and settle her stomach today and get her eating you can try either:
1) Pepcid-ac (famotidine) at one 10mg tablet per 20 to 40 pounds of body weight
every 12 hours.
2) Prilosec (omeprazole) at one 10mg tablet per 20 to 40 pounds of body weight
every 24 hours.
These will reduce stomach acid and should help her feel better.
A couple hours after the acid reducers offer a homemade diet of 1/3 boiled, lean hamburger or white, skinless chicken, all fats and juices drained and 2/3 white rice. Add warm water or low salt beef or chicken broth to get more fluids in. The more fluids she takes in the better she will feel. Small frequent meals are best.
Signs that things aren't going well, and she needs an immediate veterinary visit, are vomiting, a tense painful belly, lack of an appetite even with the acid reducers and bland diet, a fever (more than 103.5F rectally) and lethargy. If it doubt at all that things aren't going well it is always best to have her checked.
Once she's feeling well then start mixing in her regular food, adding a little more regular and less bland at each meal. It should take a week to get her converted back to regular food.
Let me know if you have any questions.