DA2 NPC straight-up calls Leliana a trickster if you mention her. Yeah, I agree Leliana is well-written subversion of your usual religious character in fantasy. Morrigan and her have interesting banter of an atheist and a religious person. She's a born again Andrastian who doesn't shy from using her charms and seduction up to participating in a threesome/foursome if you "harden" her.
Hardening her involves convincing her to give up on religion though. If you don't harden her she has no part in any of that and won't even let you do it on your own if you're romancing her. Only time religion comes up for her when hardened is she'll try to kill you if you poison the sacred ashes but can be talked down, whereas when unhardened she fights you to the death either way if you try it.
There's also changed dialogue. Zevran hits on her and when she's hardened she returns it, even if she's romanced, but if she's not hardened she's disgusted by him whether she's romanced or not. Far as the bi angle goes she seems to be written to prefer men. Other NPCs make fun of her for staring at the male PC all the time, which doesn't happen for a female PC.
So yeah, she's a slutty spy if you convince her to be one, but if you don't she sticks to being a sincerely religious cloister girl. Both of those are fetishes depending on who you ask though. If we're gonna talk DA2 we can't ignore how every returning character gets assassinated, see Anders the flamboyantly gay psycho murderer.