Does Shadowheart even have endings? I could never get her to say anything even with her being in my party for the entire game.
Nope. Only if romanced, at which point the endings are way too short (as is the case for all companions) but at least good for what we have right now (even if the dialogue choice in one of them is questionable, but at least you can just assume your character will say and do the obvious thing when it rolls to credits).
None of them are perfectly happy, majority of her lines are about the negative aspects of the choices made, but at least the conversations end on a positive note with clear indication that you'll heal together in time (unless you 'unfixed' her, at which point you deserve what you get anyway).
If you didn't romance her she may as well have drowned for all you know (she didn't know how to swim, after all), if she isn't the one assigned to give a one-liner.
