Zevran has a thing about redheads. Rinna was a redhead, so is his Warden. Keeping that in mind, there's something always a bit bittersweet about seeing her, especially since she has such a playful energy, something he associates with Rinna. If she actually swung his way he probably wouldn't hit that, but he would flirt even more mercilessly. He wants to kiss her hand. He loves her laugh and her smile. He wants to go out and ogle women with her and get totally drunk, and just bro out without having to worry about being objectified or expected to perform, honestly.

He has a bit of a misunderstanding when she talks about being a lesbian, since plenty of people are bi and gay in Thedas and it's not really a thing.