Which gives me occasion to ponder that this will leave an imbalance in terms of Love Interests. A love triangle would derail some characterization if not the plot -- but I don't necessarily think it would happen. Perhaps a character would just be left out.
So a red-haired girl started to snark and suggest various things about herself, and smile whenever pushed for her exact role in the story. Such as whether she's even interested in playing the Love Interest game.
Got to admit that she makes a better foil to the new unified girl than the old twosome made to each other.
Sometimes just throwing characters in and seeing what happens works. You end up not able to find the seams between what you introduced later, and what you started out originally. Sometimes you can't even tell whether something was a new or an old element.