"But there's no way I could match what any of you could do, is there?"

It's not that she doesn't want to, mind. Far from it. It's just... well, she of all people knows how inhumanly powerful the Servants are. And while she may have even made some efforts, in her own way, to get stronger, she's still keenly aware that even the most powerful possible human could never stand a chance compared to even the weakest Servant.