Isn't that Aoko_Aozaki

Hmm, hairstyle is definitely hers, she doesn't wear a skirt however. Maybe she stole Akiha's clothes?

Are you sure that she is from Tsukihime/Melty Blood at all?
That this is not some random red-haired girl?

Just to clarify, it is; It's one of her different outfits she wears later in Tsukihime.