Should i try formula again even though it made her sick?

My baby has been feed for 5 1/2mnths buts i have had to give her some formula due to returning to work. all of a sudden she will not drink the formula, have tried changing it and of all the ones i've tried the only one she drank without a fuss made her projectile vomit. She i try again with this one or do you think she could be allergic?