hmm... this is how i would have handled it...
Me: "anways im off to take a shower
"Her: "Dirty"
Me: "haha... yeh i totally am! i smell like man sweat! dont get smart or i'll put your face under my arm pit so you can smell man sweat!... hmmm actually wait... i wouldnt do that... you'd sooooo love it... wouldnt you you dirty little rat bag! haha
"basically it turns her shit test around by calling her dirty in a playful way...
from what i can see you just keep agreeing with her without turning her shit tests around... its ok to agree with it... but do it in a funny and playful way...
and for the "are you hitting on me?"
i probably would have said
"haha yeh totally! its because you're soooooooo my type haha :S"
it has a hint of sarcasm in it and kind of disqualifies her...
note that these work for my personality... they may or may not work for you but give them a go next time it happens