My cat keeps growling at me?

First let me give a little bit of background. I have had my cat for almost a year, I saved her from the streets in the country of Bahrain. I lived with her in a 3 bedroom apartment, and it was just us. I recently returned to the states and am staying with my family for the next week before moving on to my job in san diego. My parents have 2 cats and a rather rambunctious dog. For the most part all of the animals have been getting along pretty good, my cat tends to shy away from the other cats, but I figure that is normal. But for the past 2 days I have noticed she isnt eating, though she is drinking water, and using the bathroom. She has also been growling at me, like a dog, and snapping at me. As she is usually a feisty cat, this is pretty normal. Except for the growlling part. And today she threw up 2 times, once with food, the other with white foamy liquid (when cleaned up it turned out to be yellowish in color). Do you think she is just stressed out, or could it be something elsse?