Say him I was a CSI agent...;P
(since practical, insightful, emotional and TL;DR have been covered; i'm going with the cynical interpretation.) This could be a form of leading you on. I have seen a few people in your situation and have also been there myself. There are some who will se your good and willing nature and their first reflex is to dangle an emotional carrot they never plan on you getting. All of the talk of comfort zones and such could be a dressed up way of saying 'just keep trying'; but in a way that makes you more of a longing minion than a friend. Since you're already asking after it the hooks may be in you already. pull those things out and let her be complicated on her own time.
Friendship shouldnt be such hard work. If she thinks of you as her friend, yet doesnt let you in on her comfort zone, its like a losing battle. Friendships work two ways, where both people have to give and take, and sometimes stretch their limits, if they feel its worth having the friendship.
zZZZzz... ZZzzzZZz... Zzzz..
she either likes you or thinks you like her. what i can tell you is that no matter what person, a man and woman "friendship" will ALWAYS have sexual tension, even if it is a dismal amount. you can improve it for sure, but don't expect her to approach you as if you were a woman. because you are not.