Travellers who may be eligible to apply for an eTA:
Citizens from select visa-required countries may be eligible to apply for an eTA, instead of a visa, to travel to Canada by air. However, these travellers need a visitor visa when arriving by car, bus, train, or boat, including a cruise ship
instead of a visa. so because your wife has previously obtained a canadian visa the eta is all that is required now.
was the visa she had before in the last 10 years ?
Who can apply
You are eligible to apply for an eTA if you meet 3 requirements:
you’ve held a Canadian visitor visa (temporary resident visa) in the past 10 years or currently hold a valid United States nonimmigrant visa
you’re coming to Canada for a short visit, business or tourist activity (normally for stays of up to 6 months)
you’re flying to or transiting through a Canadian airport using a valid passport from one of the eligible visa-required countries
If you do not meet all of the requirements, you need a visitor visa (temporary resident visa) to travel to Canada.