My cat just threw up? :(?

It was very strange. 20 minutes ago, my cat and I were resting on my bed and she was purring and snuggled up against me. About 5 minutes afterward, she jumped off my bed and vomited a couple times. then she wandered off into the hallway. As I cleaned up her vomit I noticed the undigested chunks of the friskies I had given her last night. Afterwards I went to grab her, to see if she was alright, petted her a few times, and to my surprise found her purring. She then proceded to rub her head against me several times and followed me to my bed, where even now she is still purring. this is the second time this has happened. The first being 4 days ago. She doesn't appear to be in pain. In fact after she vomited she had a drink of water. But still these vomiting spouts occurred so close to each other, I'm worried that it may be something worse. Right now she's five years old and she is strictly an indoor cat (she has never been outside). She is also up to date on all of her shots. My theory is that maybe the friskies I gave her went bad? I put it on a plate and she usually eats it as she likes, but not all at once. In the winter it's okay because the house is usually pretty cold, but could the summer heat cause the friskies to spoil? I'm kind of worried right now. What do you think about it?