I can see the food trick working, but if it did wouldn't be as effective as shooting it straight down her throat. I'm not a vet of course, just an EMT and in my experience (with People) when we give them medication and they've eaten shortly before we have arrived it takes longer for it to work (of course also depends on the route).

Good luck! Almost everyone on this forum is of course more informed than I am and I wouldn't be surprised if I am absolutely wrong. I still have to find a HerpVet (found out recently that my vet was just lying to me about herps, unintentionally though)!