Leliana starts coming onto you pretty early. I think her desire to wait has more to do with her personal soul-searching and the fact that her last lover turned on her, got her tortured, etc. Trust issues.
Alistair and Leliana both clearly experience sexual attraction before any emotional bond is built.
Sorry, but as I stated in my original post, I think that is highly subject to interpretation.
An expression of affection =/= an expression of sexual interest. Neither does interest in forming a deep friendship or emotional bond. I would also suggest that, as a bard, Leliana may have the presence of mind and skills needed to manipulate someone into not friend-zoning her even if she herself is not quite ready to go there.
I can't speak for the relationship arc with a male warden, as I have not experienced it. I can speak only for the particular relationship path(s) I have experienced. Someone mentioned the 3-or-4some with Isabela, but it looked to me like Leliana went along with it so as not to be excluded from the warden's sexcapades, not necessarily because she was sexually intrigued by the prospect. She certainly displayed a distinct jealous / possessive streak when it came to her relationship with the warden.
Ultimately, what we think we observe in the behaviors of others is very much subject to interpretation. There are a couple of influential factors that I think may be worth mentioning:
1) I think women in general have a much broader spectrum with expressions of platonic affection than men generally do.
2) People who are on the "sexual" end of the spectrum are probably a lot more likely to read things as sexual triggers than those who are closer to the demisexual / asexual end of the spectrum.
And no, I'm not trying to suggest that Leliana was intentionally written to be demisexual - only that she can be interpreted as such. I don't know whether
authorial intent (WOG) should carry that much weight.
"All worthy work is open to interpretations the author did not intend. Art isn't your pet — it's your kid. It grows up and talks back to you." - Joss Whedon