I'm a bit late to the party, and it looks like the issue has already been solved, but I would have to say that this is extremely unlikely to be related to malware in any way. There is a Microsoft Office vulnerability that has been recently exploited in older versions of Office, but the vulnerability was patched in 2009. Office 2011 would not be susceptible. A Word macro "virus" could be a possibility, except that I've never heard of one of those crashing Word, and you say you haven't opened any documents from someone else. (Are you sure you didn't open any documents from your daughter around that time?)
I'd have to say some of the other suggestions are more likely. Syncing, updates, perhaps some other third-party software you installed that conflicts with Word, etc. Malware is almost never the "go to" answer on Macs.