My puppy ate a little onion will she be okay?

I have a ten week old chihuha / jack russel mix. I had a little burger from krystal's earlier and gave it to her. I thought it was plain but i saw her licking the onion on it and managed to sc most of them off. But when i looked it up online it said that onions are very toxic. Her heart seems to be beating a little faster but she was doing that earlier today as well. PLEASE HELP ME because i am about to cry im so worried