The style seems to be of the sixties. The woman seems to be in her twenties or thirties. If it is not a phantasy painting perhaps they used the wrong name? One of the daughters of the then Duke François Xavier is a possibility although I do not see a striking resemblance. None of them have the name Louise somewhere in their names though. Another option is Pss Marina de Bourbon, née Gacry, who owns a perfume label with her own name.