I figure if the elder child was about 3 or 4, then she'd be just old enough to remember Mommy but young enough to not understand the finer points of time-travel and alternate-universe counterparts.
So Clark just got 'custody' of the kids recently? That would explain how she understood 'Mommy'. I just envisioned Clark gaining custody when they were smaller.
Thanks
Mike
Create all the happiness you are able to create. Remove all the misery you are able to remove.