I'm not sure what you mean, we see them both in the same animation, they are shown as two separate people. We haven't had a single instance where a person has shown mental trauma as an externalised vision/phantom. We also know that there is a sister from the painting shown earlier. It's also not Bella's mental game, because she's talking to Nika. I also think what we've seen of Bella can be easily explained by trauma without needing multiple personalities.
I certainly agree Melanie is an interesting and important character to the plot, it'll be interesting to see what Ocean does with her.
Well, they're all now Nick, Zara and Vanessa's roomies! Everyone is 1 degree of separation from a roomie!
I honestly just mentally translate what I think the case is (from playing too many AVNs), it's like reading sheet music while playing guitar in drop D and having to transpose on the fly.