tl;dr: the science in this chapter is 100% solid. She may still be stung in the future, but it'll be much less likely to kill her than if she were to be stung a second time.
While I agree with this about allergic response, and found it weird that people were just saying "it wouldn't be worse" when it totally could be...
The whole "shout at it" part is absurd. Wasps can detect loud vibrations via their legs and antennae (especially though a surface), but responding to someone shouting, through the air? Extremely unlikely, given they lack ears.
So no, I would not call the science in this chapter "100% solid".
That aside...this chapter really seemed so contrived to me. "The person who brought us together was secretly our senpai all along, and now we're working with her, and the very first thing we do is experience a critical moment in her life and save her future"...I mean, I guess if this story isn't going to be very long, that's okay. But it's a heck of a thing to throw into chapter 6.
Also, the way their senpai didn't seem fazed that these two just so happened to be loaded with bug spray and ready to break walls down, and they just so happen to encounter a threatening wasp...it's unbelievably coincidental from an onlooker perspective.