Child allergic to one cheese but not another, need advice

I hope this is okay to post here, I’m needing some advice around ingredients. My toddler has always had cheese with no issues, cheddar and mozzarella mostly. Recently we bought these cheese sticks (knock off stringers in Australia) from Aldi. She has eaten them 3 times, and all 3 times within a few hours of eating them, she has vomited. We didn’t connect the dots until yesterday (the 3rd time). Can someone tell me the difference between the blue label one (the one she vomits after) and the green labelled one (mozzarella she has all the time). We don’t understand how she could be allergic to a brand of cheese, but be fine with everything else.