Sure it does. Carla admired, and maybe even loved, Simmons before he violated her by turning her into Ada and it's possible that it bordered on the obsessive before or after Simmons messed with her personality. Obviously, she felt hurt by what he did, which could have prompted her to do what he did - create her own "Simmons" that would never leave or betray her. It's possible that, to her, this clone would be her perfect creation. The C-virus, the J'avo', the Ustanak and Haos don't really matter in comparison to her if she can have her precious Simmons.
Of course, this is just speculation. They didn't say what it was but, with the computers telling you all about Carla and Simmons right beforehand and the fact that it was a hand that came out, I'd say that a Simmons clone would be a good guess.
^ This times a million. The final segments of Ada's fourth chapter show that Carla is still somewhat obsessed with Derek deep down. It's actually quite a tragic story and I actually feel bad for Carla somewhat.
Stupidity isn't a virus, but it sure is spreading like one!