Answers
With a legal entry into Greece, she may be granted a resident permit by her husband.
If your son is still eligible for a Golden Visa (as your dependent), his wife will also be.
According to the law, family members of permanent residence holders as property owners are considered: spouses; the other spouse or partner with whom a third-country national has a cohabitation agreement in Greece; the direct unmarried descendants of the spouses who are under the age of 21; the unmarried children of the supporter or of the other spouse/partner, provided that their custody has been legally entrusted to the sponsor (for his/her children) and to the other partner (for his/her children), under 21 years of age; and the direct relatives of the spouses in the ascending line. So following the above provisions in force, in reference to your son, he will lose his permanent residency. But you have to take into consideration the possibility to sell/transfer of property ownership through parental benefit to your son under the condition that he is 18 years old. Under this scheme your son as main investor, his wife and you as parents will be entitled for Golden Visa privileges. For the legal part and steps of the above procedure, you have to ask for a lawyer's advice.
As per current legislation, the Golden Visa, which is issued pursuant to a real estate investment (i.e., property at minimum cost of 250,000 euros), will be valid to the owner(s) of the father, mother and children (dependents) up to 21 years of age and grandparents. Any dependents exceeding the age of 21 years will be required to make their own investment in order to continue being eligible for the Golden Visa under real estate investment, and this goes for their spouse. If the property is valued per contract at 500,000 euros and above, it may then be divided (50 percent may be transferred to the dependent) so this same property can offer eligibility to the dependent who is over 21.
Please clarify if your son is underage (18 years old) or above. In the second case, he will need to apply for a Golden Visa for himself and his wife.
That is the question! In few words we build our path. It is a step-by-step procedure.
He can keep the resident permit, but his wife cannot receive one because of him.