Um, Lois wasn't Lex's fiancée yet when he offers the copy of her apartment in the bunker for her to stay.
From Chapter 7:
She was so deep in thought that Clark’s voice surprised her. “Do you know Lex Luthor?”
Her answer was abrupt. “We both do. I've interviewed him and since then I've accompanied him to a few charity functions.”
“So you're dating him?”
“No, Clark.” She was trying to figure out what was going on with Lex. This was irritating and she was only half-way paying attention to what Clark was saying. “There isn't anything personal to our relationship.”
It isn't until after the Planet is destroyed by the bomb in the show that she accepts.
malu
