Dual Citizen with expired passport

Here to get info for a family member who's born in Canada and has citizenship, but passport is expired. She's a Swedish citizen as well and will be travelling to Canada next month. I'm assuming she can't apply for an ETA (I read somewhere that dual citizens can't get an ETA). Is a Canadian passport or emergency travel document mandatory or can she get into Canada any other way, such as other proof of citizenship, ie. expired driver's license, expired health card, etc.