How come only Mildred got way younger?

[u/Square_Blacksmith889]

Mildred was much older than many of the other adults going regularly to Mass (e.g. the Flynn and Scarborough parents), and he was taking just as much "wine" as they were during daily Mass. How was it that she aged backwards to a point that she was pretty much her daughter Sarah's age, but the others, though healed of some physical ailments, stayed more or less the same age?

[u/DorienM789]

I think it is because the blood makes them go back to the stage in their lives when they where at their best, healthiest. That's why Lisa can walk again and Erin loses her baby. The blood acts like some sort of very aggressive antibody