First look at your kitchen, supply closet, bathroom to see if she ate anything toxic. Anything with chew marks on it, that she could have gotten into. Foaming at the mouth can mean she ingested poison. If this is the case, take her to the vet immediately so they can pump her stomach.
Cats will also foam at the mouth if they are nauseous, or about to throw up a hairball. Watch her, and once she does this, clean the area.
Your cat could also be foaming because it ate an insect, or bit a frog. Some animals emit a substance that will be extremely bitter and will make animals foam at the mouth temporarily.
If your cat does not have the rabies shot, this could also be indicative of that.
Cats will also foam at the mouth if they are nauseous, or about to throw up a hairball. Watch her, and once she does this, clean the area.
Your cat could also be foaming because it ate an insect, or bit a frog. Some animals emit a substance that will be extremely bitter and will make animals foam at the mouth temporarily.
If your cat does not have the rabies shot, this could also be indicative of that.