Isabel Preysler and Tamara Falcó seem to have no intention of sharing power. The announcement by Disney+ of areality show about Isabel reinforces this argument.
For the younger generations Isabel Preyser is Tamara's mother and not the other way around. There is no room for speculation as a product of the era of reality shows. What you see is what there is and you see it at all times in all places, in all times, in the list of children of Isabel.