No, his wife cannot get a Golden Visa.
How could my son keep his residency permit and reunite with his wife in Greece under the Golden Visa program?
My 17-year-old son got his residence permit as my dependent. He just reached 20 years old recently and got engaged. After he gets married, would he lose his Golden Visa? Can his wife get Golden Visa too？
Children under 21 years of age, parents, spouse or partner with a cohabitation agreement concluded in Greece and in-laws of the main investor can benefit from the same investment of 250,000 euros and above and issue a permanent European residence permit too. So when your son becomes 21, one easy way is to transfer ownership of your real investment to your son, and your son, his spouse and you as parents could get Greek Golden Visas.
Family members of the main investor are the direct unmarried descendants of the spouses, who are under the age of 21. After that, it is possible to acquire a renewal as an independent residence permit until they reach the age of 24 and then it is possible to renew it further according to pertinent immigration legislation. But since your son is going to be married, one of the above conditions cannot be fulfilled anymore. In such a case, if you don't have other children, already included in your application, and in order his wife to be also included as his family member, you should examine the option either to sell your property to your son or to transfer it through parental concession, after examining in advance the tax value of your property.