As I said several times before, the only reason why I think MC will/should not turn her is that MC's clan is one of the plot drivers. Another one like him would make him less special.
au contraire my friend...
1) dealing with the thing in the woods and twarting the plans of the hunters would put the MC past the fledgling stage and he would be recognised as a full fledged vampire, no longer needing Sharon to babysit him, so any sin he committed would not befall on her. he could kill an archon and no one would accuse Sharon, nor the Archon could use MC's failures to try and "punish" Sharon. he could stake Astrid and Sharon would not be blamed.
2) turning Carmen would deny her the opportunity to be reunited with the ones she loves while giving her an eternity to fall in love with the MC. this would make Sharon less certain of her position and maybe she would try harder to impress him.
3) by turning Carmen, the MC could become the progenitor of a new clan. Carmen is not the MC so she might not gain the same powers that he does and could awaken a different set of powers, that would indicate that MC could have those powers too, and that would make his lineage more special.
4)Carmen could be somewhere in between Sharon's selfcontrol and Astrid's YOLO... immagine all the kinky things MC could do with Carmen...stuff that would be too cruel to subjugate sweet Laurie to. I'll propose a plausible dialogue...
Sharon: you want to do what? no way in hell. [she walks out of the room slamming the door behind her]
MC: Carmen, get on all four.
Carmen on all four : mhhmmm mhhm mhmmm ( a ballgag is muffling her words)