[Applejack is about to snap back about the scared part when she stops herself by reminding there's another reason she's asking for his help. That doesn't mean she can still add a bit of sting to her words though.]

Busy? Busy doing what? Making those zombies do a hoedown for you?

Look, Ah need to check on my friends, and Ah don't think they'd appreciate if Ah came calling as a zombie, so Ah'd be grateful if someone came along to watch mah back. We can check on your friends as well, make sure they are safe or even get them here if those wards of yours are so strong. If you can handle them so well, it shouldn't take you what? An hour or two?