IMO, you will never go wrong sticking with Louise! She is awesome waifu material! (On the other hand, if you want to explore some of the other LIs, you HAVE to break up with her.)
That said: it is not fully realized yet, but there is every indication that some kind of throuple/poly kinda thing will be possible with Louise and Nurse Dani. It is unclear whether it will be long-term/permanent or just a one-off. I think it's safe for you to start something with Danielle though. Just don't be a jerk about it. (You know? Be honest with everyone?)
These two are definitely my favorite LIs in this story, but the others are all attractive in their own ways as well. I didn't think I was going to like Cindy at all in the beginning, but she has grown on me. We don't know Cassandra very well yet, but she's looking interesting too. Then, there's Kimiko. She can be your (surrogate) baby girl, or she can be your Baby Girl. Each approach has its merits.
This game is meant to be replayed on the different paths (and with different sanity levels) to get the full picture. I have some theories about the "big picture" that I'm very much looking forward to seeing how close they are to the Truth.