Cat vomit and won’t eat

Hello, my cat is 10 years old and is a female, and as the title says she puked breakfast out and now will not eat and her behavior has changed. Her vomit was whole like nothing digested, and she did not what to eat dinner. I’m a little worried because she is always eager to eat and gets very excited when we feed her. She’s now under the couch instead of trying to sleep with me in the bed , which I know can be just her not feeling well. I already plan on calling the vet in the morning but I was wondering if anyone has any advice for me? We changed her food around a month ago and has been fine on it until today