"Quick! Take off your clothes!"

My roommate dislikes my mother. At least this is what i think from the way she acts when my mother comes over to the house, giving reasons why she needs to leave, rushing around and then out the door, etc. This is an issue, because my mother is also our landlord.
My roommate tends to fall on the passive-aggressive side, and likes to plot against people who don't even know they're the enemy. At one point, she came up with the idea that maybe if someone was naked when my mother came over, my mother would learn to at least call ahead before she showed up. She then volunteered that my boyfriend be the naked one, which gave us all a laugh (at first). We didn't think she was serious. Now, whenever my mother shows up, my roommate yells for my boyfriend to "Quick! Take off your clothes! Hurry!" and really expects him to do so.

She only quit after I told her it wasn't very appropriate for someone to order someone to strip naked, and perhaps she should try "using her words" to ask my mother to notify her before coming over. Did I mention she's over 10 years my senior?