I'd venture to say she'll be ok as an old neighbor of ours years ago used to home cook for her small dog everyday. Every single meal she'd add ONIONS ot her meal, said her dog loved it. I tried and tried till I was blue int he face to tell her they were toxic to dogs but she wouldn't listen to me, she was older and set in her ways and wouldn't have a younger person telling her anything
We were here neighbor for almost two years and in that whole time, she was at the vet almost weekly with her dog being very sick. So, if her dog can go for that long eating onions throughout the day, I'd say the very little amount your lil one had today won't hurt her. The best thing to do though would be to cal and ask your vet. Good luck.