Morvern and Lanna - !Spoilers!

I watched this movie last night and when it finished I didn't think much of it. However, I cannot stop thinking about it now. I woke up this morning thinking about the film and I realized that perhaps Morvern and Lanna were the same person.

Morvern is clearly distraught over her boyfriend's suicide, caressing the body, leaving it in her apartment while it rots, then finally cutting it into pieces and taking it to a field for burial...

Although the way she treated her boyfriend's body and the novel that he had written wasn't very...grieving girlfriend-ish, she had clearly lost it.

I believe finding the body of her boyfriend was so overwhelming that she disassociates herself. Her personality splits and Lanna is formed. Lanna is much like Morvern, she's care-free and fun-loving, but there is one distinction: Lanna doesn't know the boyfriend is dead. Lanna was created to help Morvern cope with her loss. In fact, when Morvern tells Lanna that the boyfriend is dead she doesn't even react to it, she doesn't want to know.

Morvern and Lanna are very close. They work together, bathe together, visit Lanna's grandmother (even when Lanna isn't around - odd). I don't recall that at any point in the film they had both interacted with any other characters simultaneously. Either Morvern speaks or Lanna speaks, never both.

Lanna disappears for long portions of the film also. Most notably when Morvern leaves Lanna in the field in Spain by herself (with no luggage). She later appears at a bar Morvern frequents and they decide to go their separate ways. Maybe at this point Morvern has come to some sort of resolution with herself and her boyfriend's death. She's ready to move on.

Any other thoughts on this? Am I wrong thinking that there is more to this story than it seems?