You can also give her gifts and most of her gifts are bought or found easily. She will not appreciate you insulting either or questioning her faith. Even if you don’t like the chantry or believe in the Maker, she does. Agree to listen to her stories and compliment her storytelling abilities. You can just talk to her and be nice for the most part. Gaining approval with Leliana is very easy. You just have to say that you want to talk. You have to love lines about “forbidden fruit.” If you mess things up somehow, you’ll get another chance after you finish her companion quest. Male wardens can make some horrible pickup lines after asking why she was in the chantry. To start the romance with Leliana, you need to flirt a bit. Even if you “harden” her (see below), she will need a special conversation path to talk her out of defending Andraste.
If she’s not there, then you should be able to lie to her and convince her otherwise. She doesn’t like that and will attack you if you defile Andraste’s ashes. Just make sure that you don’t side with the cultists during the “ Urn of Sacred Ashes” quest. I had her at 100 about halfway through the game. Winning Leliana’s heart is actually pretty easy.