What is the ruling regarding the prayers of a woman in the past who was unaware that touching the private parts invalidates ablution?

Scholars have differed on whether a woman touching her private parts invalidates her ablution or not. The Shafi'is and Hanbalis held that it does invalidate it, contrary to the Hanafis and Malikis (with details in their respective schools). Since the issue is a matter of scholarly disagreement, it is permissible for a woman to follow the opinion that it does not invalidate ablution, especially if she is in a country where the Maliki madhhab is prevalent.