My oldest son used to make himself sick when he was this age, and older.
In his case, like honeybunny's ds1, it was when he was put down in his cot. Sometimes he used to get very upset if he knew it was bedtime, would deliberately start to hiccup in a certain way and this would cause him to spew up. I never saw him with his fingers in his mouth, but the effect was still the same.
I can't offer a solution, but can say he grew out of it, and was never underweight, despite 'losing' his supper quite often for a while. The sickness tailed off and by the time he was four it was no more. Sorry, that sounds a long time when you have a 1 year old, doesn't it!
I mentioned this vomiting problem to the doctor several times so he could keep track of it, in case something more serious was afoot. I also tried to give ds little attention when he was sick, apart from a quick cuddle when I had cleared away the mess. I wanted him to realise that being sick did get him what he wanted. However in your case, I would think it's no good forcing your dd to continue to eat her food after she has been sick. So I agree that your best bet is making no fuss, and waiting for the next meal. Also watch her milk intake at mealtimes - my ds was more likely to be sick if he had milk and solids together.
However, if you get really worried that she is eating so little, how about keeping your dd topped up with small healthy snacks and actually doing away with proper mealtimes for a week or so? and trying different foods - dry food is easier to digest - when my ds would eat nothing else, plain ice cream wafers went down well (not vey nutritiuos but at least it got him back into the habit of eating food). You could still give no attention if she makes herself sick, but at least you would have tried a different method of feeding her.
Hope this is a short passing phase.