Promise Of Destruction

Just keep going to talk to her. Convo's with her never happen in the same order, which is annoying. Main quest talks might take precedence over her personal quest, the high approval quest (Guilty Pleasures) can trigger well before either of her other two quests. The only time I know what convo is going to happen is when I see her sitting down instead of whacking the models.

You could try doing Wicked Eyes, Wicked Hearts first and then going back to talk to Cassandra.

I've played DAI many times (indeed I have seven world states, one from each race of Warden including the human and the elf versions of Magi origin. They're all in various different parts of the game) and companion quests sometimes vary in between which Main Quests they show up on. Some, like Blackwall's, are fixed until you've done both and the Temple of Mythal is next but others are more flexible.

Sometimes Cassandra's quest would pop up between HLTA and WEWH, sometimes after both. Same with Cole and Solas' I've always had Iron Bull's between HLTA and WEWH.

It also seems there might be a set limit to how many companion quests you can do at certain points in the game. If you're between HLTA and WEWH and have already done a lot of companion quests it might not let you do more until you do WEWH.

So, how many companion quests have you done?

And my general advice is to talk to Cassandra, exhaust every dialogue tree with her. If that doesn't work, try doing a quest that has you leave Skyhold even if its just a trip to the Black Emporium. Just a map change. Then try again. If that doesn't work then do WEWH. Though admittedly if it doesn't trigger after that I'm stumped.