The Right Side Of My Dog's Face Swelled Up And She Won't Eat Or Drink. My Family Thinks It Might Be A Spider Bite. Can You Help Me?

You should see your vet in this case, in the mean time you should monitor their respitories (breathing). You should be concerned and bring your pet to local emergency pet clinics/vets if they start to breath with their mouth open, breath very fast or seem to have trouble taking a breath. If you only notice swelling and the rest of their behavior is normal, you can protect them from allergic reactions to things such as spider bites by giving the dog ONE MILLIGRAM of PEDIATRIC BENADRYL per each POUND of the body weight. This is accurate for small dogs according to my vet, but I would contact a vet or clinic by phone to confirm this dosage. AND TO CONFIRM YOUR DOG DOES NOT HAVE OTHER SYMPTOMS THEY ARE CONCERNED ABOUT that may signify other issues.
The way you calculate the ONE MILLIGRAM PER POUND is as follows:
Example
the childrens benadryl says
12.5 mg of "specific medicine" per dose
a dose is then further specified as 5ml or one teaspoon

this tells you
one TEASPOON (be sure not to confuse your tablespoon and teaspoon measurements!!!)
has 12.5 mg of medicine.

So

a 3.5 pound chihuahua would need 3mg of medicine, and therefore should be given just UNDER 1/4 teaspoon of medicine.
(according to my vet you should give 3 mg for a 3.5 pound dog, its one milligram per pound and you round down)

you should contact your vet or local pet emergency/medical clinic for frequency of doses.
You should alos bring the pet in to follow up with your doctor.