First stomach bug, worried about dehydration

Our 9 month old had been vomiting up formula for about 8 hours now. She will promptly vomit up any bottle we give her shortly after being fed. She has no fever and doesn’t seem incredibly uncomfortable or lethargic; but I’m worried she’s dehydrated bc she can’t keep any liquids down. The pediatrician suggested pedialyte in small doses to see if she keeps that down. First time mom here so of course I’m worried to death that I should be taking her to the hospital. Any help or advice is very much appreciated!!