Questions on babies second possible food trigger

I have an 8 month old who had a severe fpies reaction to dairy on both the second and third times she had dairy (had formula once with no reaction, second time she had formula had a mild reaction, third time she had yogurt the reaction was severe).

With her second reaction to dairy we ended up in urgent care because she was throwing up/gagging non stop to the point of throwing g up stomach acid and became lethargic. I think the reaction was also so severe because of the amount she ate?

Last night she had a suspected reaction again. It was pretty mild compared to before. Only threw up 3 times, did not become lethargic, no diarrhea. Is it possible that different foods have varying degrees of reactions? Or different amounts of foods have different reaction?

Yesterday she had eaten egg cooked in olive oil with carrot and zucchini. Should I try all these foods separately to see what was the trigger?

What are the chances it’s not fpies and maybe just had an upset stomach? Maybe this is me just trying to be hopeful. Any similar experiences?