Faith could certainly sneak Harlan some Bliss. She's shown to both blow it in people's faces and put it in drinks or tea. It makes anyone who has it, for the most part (there are people who are kind of immune but it's weird), hallucinate that the world is much more beautiful than it is. Lots of butterflies. It's almost as if the world has a soft smoke/fog filter on it, with lights brighter.

As of right now, she has a small amount of the powder, dried flowers, and is attempting to grow a small field of them. She could mix some of it into a drink for him at some point? She'll have to have a reason to do so. For instance, his mental health during the deserted event is enough for her to consider using it just because she knows it can provide momentary reprieve.