I apologize if this a simple question, or one that has been answered previously.

I am flying YYZ-FCO later this week for work. The ticket was booked in Z class by my client. I want to bring my wife along for part of my time in Italy, but don't want to spend the $7K it will cost to book her a business class ticket.

Since I can't "cash in" my ticket for two economy ones, I'm obliged to buy her own ticket. We can book on points for 60K (+$650 taxes) or buy an economy ticket for ~$1600. I have eUpgrade points, but want to know if I can use them to upgrade her fare if I buy it as a reward ticket. Or if I should book the Flex ticket and try to use my eUpgrades to upgrade her on the day of travel. Or finally, should I buy a Flex ticket and hope the system offers the "for sale" upgrade at check-in. I'm E35K.
Any advice you can offer on how to give myself the best chance at upgrading her would be appreciated.