To be fair, all DOA characters are hated by someone. For example, I hate that random middle-aged guy who groped Leifang on the train in DOA4 (and almost in the subway in DOA5).
Who knows. Every character can be annoying in their own right. Likely some just do it easier than others..and difficulty varies depending on player if they understand the Mila matchup or not. It really depends.
@DestructionBomb: As someone growing up in the 80s, I find nothing really wrong with Mila's theme. It seems fitting for her character, and heavily inspired by Vince DiCola's style of music, who also wrote the score for Rocky 4 and the 1986 Transformers movie.