No, I think that's true. She does get tagged, fairly aggressively, as Lucy when she appears, and in some ways the book follows that (first victim, victim whom the FVH conspicuously fail to save), but in other ways it subverts it. Clemmie has far more agency than Lucy, and she has her own agenda. Her helpless femininity is a pose, not the truth of her. Although I like your point particularly for the way in which Evangeline and Clemmie's affair then becomes the overt textualization of the subtextual homoeroticism between Mina and Lucy.

(I picked up Fangland based on what you were saying about it at Penguicon, so your recommendations are bearing fruit.)