What can be making my cat sick?

My cat has been vomiting for about three days now. She eats purina naturals wich is not part of the pet food recal. She has been throwing up for about 3 days. We tried to take her to the vet but she flips out when tried to be put into a cage to take her. She was a stray before we got her and PETRAFIED of anyone and anything she is not used to. She is about 15 years old now. Just trying to put her into the car or into a box to get her into the vets sends her into a fit. We are affraid she will have a heart attack just geting her to the vet.