Hmm, keeping in mind that we don't even know if anything was missing, but maybe because something in the vehicle (a laptop?) was missing?
Was the side door on the side where the driveway is? Was someone breaking into the vehicle to get something, she heard a noise, went to the door to look, and thus the hypothesized initial altercation at the door? She's chased upstairs (carpet from stairs missing), perhaps to get to her baby, but is caught up to at the office bedroom. Or something like that. It's even possible in this scenario that she actually was conversing via email or instant message with a coworker, mentioned she heard something and was going to check, and her not coming back is what alarmed the coworker -- if that rumor turns out to be true.
These are all assumptions and unconfirmed, but good questions to think about I think. Bottom line is, we need more facts.