Starpoints can be transferred from one SPG account to another with the same home address. If you and your wife were to have separate credit card accounts you would accumulate Starpoints in separate SPG accounts, but you could transfer points between them as required. This is done by telephone (or using spg.com interactive chat feature).
awesome news. they don't limit it like aa or ua does where there is a max in a year that can be transfered? other then that i'm good to do a new, separate, am ex spg for her.