Weird, that's all I did to get her as my assistant, I think I tried to interact with her first before having sex with her while she was unconscious. If I remember correctly, she woke up either during or after having sex with her. I then talked to her and she joined my party.
Viewing post in Prerequisites for unlocking Tori.
Yeah I think splashing the water on her might lock you out of it. You probably need to reset recruit data. Apartment map data might work, but I wouldn't know for sure, recruit data is a safer bet.
I've never gotten around to splashing the cum water myself, but I was planning on doing that. Fortunately for me, I wanted to see if it was possible to have sex with her when she was unconscious first, so I inadvertently saved myself from having to reset.