Bringing up milk

My DD will be one in 5 days and is on 3 meals a day, snacks and about 450ml of aptamil. She's fine with normal food but since yesterday she has started bringing her milk back up and not the food. She's fine in herself, she's crawling around, getting into mischief and her temperature is fine. I just don't understand how she is fine with all foods and liquids apart from the aptamil milk (she is still on stage one but once she's one she will be transitioning to cow milk and growing up milk). Should it be something I see her gp about?