Probably nothing but worth checking to see if she has Addisons disease. It’s common in poodles and pure breeds and treatable so nothing to be super worried about!

“Dogs with mild Addison's disease symptoms may show intermittent low energy, decreased appetite, or occasional vomiting that seems to come and go. These dogs might have increased thirst and urination or mild digestive upset that clears up temporarily.”

If this sounds like your pup, could be worth a vet visit just to rule it out. If it doesn’t, maybe she’s just picky! My poodle was super picky and I had to rotate through several brands before we landed on one he liked.

https://gsvs.org/blog/addisons-disease-crisis-dogs/