Unfortunately I can't find her at any of these spots. I assume there must be some conflicting locations between the Lucille and Mary questlines so she isn't showing up at either of them.
For me, she shows up in the Homeless section in the mornings, the Monastery at noon, and the Cathedral in the evenings. If she's not there, then she's probably tied up in one of her Quest objectives or you've asked her to accompany you and she's waiting at the city gates.
If none of that works, then IDK what to tell you.