Hi, Just Wanted To Ask If My Daughter Could Possibly

Hi, just wanted to ask if my daughter could possibly have a fish allergy. As each Time she's had fish she's been sick. Not a lot just a couple of times then she'll be fine. Her temperature is normal 37.5
She had Youngs fish cakes last night, and on Friday at school its fish day and age said she had 1 fish finger. Not sure what type of fish was in it but I am presuming cod. She's had fish from the chip shop and been fine and we know that has been cod as it costs more, and has been fine. Please help