Hi...just catching up here. That much vomiting is concerning. Things like dehydration can happen quickly, but you also do not know if something is causing a blockage that could potentially be a really big issue beyond the blood glucose levels.
I would take her to an ER and let them assess it and go from there.
If she is blocked, unfortunately you may make it worse by trying to feed her.
I am sorry to come in, unintroduced like this here, but am so concerned for your baby.
My name is Kimmee and my cat Abby was diabetic, diagnosed in 2006 when I found this board.
I have been on this board for many years and have rarely seen a cat vomit like this.
Please let us know how it goes at the ER and do let them know how much, and how long she has been vommitting.