Isn't speed supposed to be part of her wind powers making her one of if not the fastest in Gensokyo?
Can't say I've played Shoot the Bullet, but I'd have guessed that speed and the ability to dodge allow her to survive annoying the higher tier characters. So I don't mind it so much.
PoFV was her introduction wasn't it? So having her as a stage 7 boss over other characters doesn't really bother me too much, Medicine got the same treatment and she's a newbie Youkai. As for people she beat because she's a play character... well I beat the game with Cirno. So yeah, I don't look into that too much.
Not played Mountain of Faith either, but I remember she's got a fairly good reason for being there seeing as it's where she lives. As for 'letting' the hero win, well I'm sure she would say that...
Until ZUN does something utterly over the top with her, I'll just assume she's a highly powered joke character he happens to like.