This is just my understanding of Vampire society in VTM (which need not even be the exactly same situation with Rebirth world, but as is the main inspiration I assumed).
The way I see it, being enthralled creates a master/servant relationship that is almost unbreakable. Servant almost never will go against master.
The control a vampire sire exerts on her child is weaker than one achieved by enthrallment. Even in Rebirth you still have the option of MC desiring to kill her sire (only way I would kill her is in bed If I manage to get a boner).
With these two elements in mind, assuming MC is sire of Carmen while Laurie remains enthralled, we could establish a transitivity order, where MC control over Carmen being weaker, allowing more independence, or a greater "status", as she is less a servant to MC than Laurie.
Of course, you need not have a complete order, and there could be no comparison between an enthralled human and a vampire child. So don't take my comment too serious, is more wishful thinking.
Reasons why I think Carmen having the upper hand is more interesting than the other way are the following:
while Carmen obviously not, Laurie already adores the MC, even before enthrallment. So she receiving what I think is a lesser position would allow for a more active Laurie, fighting constanly for the attention MC now gives to Carmen. I mean, let us be honest, Sharon position as MC Queen can only be taken from her by MC's sire or the beauty in the red dream. But Laurie could try to become MC best right hand, position that could also be taken by MC's vampiric child Carmen. On the contrary, a position in which Carmen has both a lower status and a lower affection to the MC would make the fight too unequal, with Laurie dominating Carmen over MC's attention/love. And I want a Kitten fight!! I want conflict!! I know, I am a monster. What can I do?
Disclaimer: out of the many female characters in the game: Sharon, Laurie, Carmen, Astrid, MC's sire, the beauty in the red dream, Laurie is the one I care less. I tend to dislike "obviously in love childhood friends", and Laurie kind of fits that description. Her relationship to MC is stronger that simple friendship and it never felt to me as brother/sister relationship. So yeah, Laurie is last in my list.