0 trust drugs are possible. Low trust just means 'Mary' can't 'exit' the city through the sewer entrance and can't 'enter' the city through the basement. That does not mean the inverse is true. Aura just needs to talk with Liliana to unlock the disguise, use the sewer entrance once to discover it, exit, and go back in. The teleport beacon also allows you to be in disguise. Spells do have trust requirements though.
The corruption condition is not having a nearby lightsource. Radiance turns Aura into a lightsource but casting fire on nearby torches also works.