Carol is a hard person to read. One of the first physical descriptions we get is of her eyes—they are "gray, colorless, yet dominant as light or fire" (3.30). If eyes are the windows to the soul, this is definitely a good way of describing Carol. She's gray and colorless because she is really hard to understand and probably a lot less interesting than she appears to be. Mysterious people are often kind of boring once the mystique is gone.
Dominance is one of Carol's, well, most dominant personality traits. She borders on condescending when talking to Therese at the department store, taking advantage of her submissive personality. She treats her as if she can't do her job: "You won't make any mistakes, will you?" (3.47), she says. No, ma'am.
That patronizing attitude might turn some people off, but not Therese. She is attracted to Carol's sturdy assurance. One thing Carol says is, "I don't change my mind" (19.87). Since you can count the number of times Therese has made up her mind on one hand, she is attracted to Carol's certainty. Opposites, as they say, attract.
That said, it's difficult to tell why Carol is attracted to Therese. What brings them together is one of the few times Therese makes up her own mind and sends a Christmas card to Carol. It's not a socially acceptable move, plus it's out of the blue. And Carol loves it. She needs someone in her life who is a little wild, a little out there, and who can grab the reins every once in a while. Therese is that person.
It takes a long time for Therese to break Carol's frosty shell, though. She keeps up the patronizing attitude for a long time, treating Therese as a doll. When Carol says to Therese, "I make sense and you don't" (11.90), we're surprised Therese doesn't slap her. It's a bold statement, to say the least, and super invalidating of Therese. Carol is so used to saying things like this, though, we wonder if she treats her daughter, Rindy, this way, too. In fact, we figure she must.
We never see Carol interact with her daughter beyond a few phone calls, and the most telling interaction is with the detective. Carol blurts at him "My child is my property!" and he responds, "A human being is not property, Mrs. Aird" (19.45-19.46). So we're figuring Carol really loves her daughter—and also doesn't see her as quite as complex and legit as she sees herself.
This reality check from the detective is exactly what Carol needs, and it's the beginning of the role reversal between Carol and Therese. This is when Carol asks Therese to drive, an action that is metaphorical and literal. When Carol returns to New York and loses custody of her daughter, it might be the first time this woman has ever lost anything. It's a sobering moment for Carol, and it forces her to reexamine her life and her priorities. She's been a wife and mother, and she might now put her whole self first because she's all she has left.
It also puts Carol in the position Therese is in at the beginning of the book. Carol takes a job, she gets an apartment by herself, and she's lonely. Just as Therese reaches out to Carol in the beginning, at the end, Carol reaches out to Therese, and she's in the unique position of seeing if Therese will answer her. Before, Carol was the one to say yes or no (and to always show up fashionable late). Now the ball is in Therese's court.
Because Carol only truly appreciates Therese once she's been knocked off her high horse, we have to wonder how long their relationship will last. Once she re-establishes her own identity, will Carol keep Therese around? Or will she discard her like an old doll?