ok, so I'm still a little confused here..
no surprise

If you don't find the woman attractive, but she's nice enough, pleasant to be around, that kind of thing, then say so. <-- that you have more of a brother/sister feeling for her.
There isn't a woman on the planet who won't appreciate this, since you've basically just stated that you want to be there for them like a brother would for his little sis.
And if you just don't like the woman period, them my previous post still stands --> why is she even asking you out?
Is she dim?
Did you lead her on? (because then frankly; you screwed up, you burn.)
*needs.more.input.to.process.correctly* :brokencomputer: