Morrigan is, Lilith is just there during Morrigan's Darkness Illusion move.
Morrigan's 4th color is based on Lilith Mode Morrigan from Marvel vs Capcom, where she has Lilith's colors, although her hair is dark purple instead of light purple.
However, Capcom said they may do DLC characters for TvC, and since Lilith already has a character model, I wouldn't be surprised if they added her.