Just a suggestion, you should print out a list of foods dogs can and can't eat. I know that there's a thread here that gives you a list as well as some links. You didn't know about the onions, so that should tell you that there are probably other things you might be giving her that she shouldn't eat.
I hope she starts to feel better and you can get her back on track.
There are only two rules at my house: House rule #1. Cats rule. House rule #2. See rule #1.