Lyssia can be romanced and married. To initiate this romance, there are two prerequisites:

1. You must have spoken to her at the Eldergleam Sanctuary.

2. She must have told the story of Elara. This dialogue becomes available after a series of personal dialogues, accessible under the "Let's Talk" dialogue option. These dialogues unlock every three days, although they require the completion of a quest between each. Elara's story is the 7th dialogue, so a minimum of 21 days is needed to reach this point.

Once these prerequisites are met, speak to Lyssia to start the romance. After the romance quest ("A New Beginning") is finished, you can propose to Lyssia. The marriage process follows Skyrim's standard system. So, speak to Maramal, equip the Amulet of Mara, and then see what Lyssia has to say.

Are there "options" for fade-to-black scenes?