Why my cat is throwing up foamy substance?? She won't eat drink or come when I call her... Help please!

There are different reasons for foamy substance sometimes it is due to constipation from hair balls, your cat may need the treatment for that.
Second reason could be poisoning or allergy to a substance, open her mouth and check if her gums are purple if so the vet will recommend a treatment.
Another reason for foaming is a seizure and again check with your vet.
Please don't ignore those symptoms.