I have no idea who this is, and do not expect that she is someone who should be giving out this type of advice.
Its a very European view of marriage. It doesn’t matter who the husband takes to bed—the wife has the ring, the respect and the place in society—her children will inherit the estate. The bimbo will be out in the cold—BUT if the wife moves out—the bimbo can move in and take over as wife #2. Its about family—its about your kids.