Originally Posted by
andredistel
..but SQ booking system is not quite as open as that of other Star Alliance members and they can't waitlist me..
Actually KF is more open that all other systems in the *A with the exceptions of M&M partners and UA as you can even use eVouchers to upgrade SQ flights.
But as others have noted that your wife would beed to be on a B,Y, or S fare to be even eligible for an upgrade.
Wouldn't it be easier to simply get her an award in Biz to begin with?