I wonder why is that Alexis drugged Louise. I guess she was trying to hid a secret and eventually Louise revealed that she was the one responsible for some kind of car accident probably implying that Alexis is a ghost of some kind since she looked rather shocked.
shareAlexis isn't a ghost. A lot of people also thought Nona would turn out to a ghost, or even the ghost of Sasha, but that wasn't the case. Alexis is simply paralyzed from the hit and run and her deal with Gavin keeps her able to walk. Gavin wants Louise and Brian separated using any means necessary, which includes making Louise look like a drunken fool.
( spoiler alert)Louise saw Brian and Alexis in the theatre and felt to the trap of Harlan Moore
I believe Alexis drugged Louise to give her a taste of her own medicine. She drugged her so she'd be unable to move, and approached her with a large knife. I think Alexis wanted to take the use of her legs away by either cutting her tendons or another important area.
We've met before, haven't we?