I believe you said she has a NEXUS card - and it seems she is not a dual citizen, so the NEXUS card should be an acceptable proof of both identity and citizenship if the original documents are lost - not to mention the card should allow for her to easily travel back and forth between the US & CA with no passport.

Agree with GUW to delay as long as possible in reporting such documents as stolen - can result in all sorts of bureaucratic nightmares if they are found and returned to you and then you try to use them in some other situation.