[@Stern Algorithm]I agree with all that [@LuckyBlackCat] said. Then to expand upon the villian. I would say causing a reaction in the middle of a battle would be not the best choice because her jumping around and fighting would only deplete her limited air that much faster. I would say doing this would be a last-ditch effort when she has no other option. 

Also thinking about it, with best Staples which are not even remotely part of the original quirk. Your character's body is probably not designed to be at maximum strength all the time especially with the Staples getting infected or can gangrene. I just don't see how someone going to be at max strength all the time and not burn out because it only comes out when there's a foreign antigen in her body.

I would recommend that she has enhanced strength kind of like Captain America levels normally. Because there's always white blood cells in the body. When she introduces an antigen to herself she can get even stronger. And again the allergic reaction being a last-ditch effort