I voted NO. I don't think she has a clue.
Now, I have not seen the episode where Rikki leaves but from I understand Danny hasn't told Lindsay about Rikki. Has he?
And I think putting Danny and Lindsay together now would be a BIG mistake for both of their characters.
Lindsay has struggled with her feelings for Danny for a long time. She thought she shouldn't be liking him. She told that to Mac (sorry I can't remember the name of the episode
) It would, to me, make her seem weak and desperate. I don't that is how the writers and her fans want her to come across. If Danny and Lindsay get together as a couple, it would make both of them seem like they are second best. Not the best way to start out any relationship.
She couldn't tell him when she was leaving to go to Montana and she didn't tell him when she got back. I think she wants to like him but is afraid to go out on a limb to be with him so she's holding back.
This in turn was frustrating Danny...
He liked her enough to ask her out, but she stood him up. Again, she wouldn't talk to him about how she was feeling about all the stuff happening in Montana so why should he open up to her about the stuff with Ruben and Rikki?
From what I have seen, Danny is a pretty stand-up guy. I don't think he would have slept with Rikki if he thought he was cheating on Lindsay. He and Lindsay slept together once and nothing more has been mentioned about their relationship.
So, I think Lindsay has no clue and if Danny really does care for her, he'd tell her. That way he can begin to have some closure on not only Ruben's death, but his relationship with Lindsay.