Favors with a good sideeffect

Just reread Mari Amwithig of Merinita's character sheet, one of the iconic characters for 5th. Edition.

What are the community's views on her flaw: Favors (her parens, for Longevity Potion - a ritual which gives a -14 bonus) ?

Is this fair? A major flaw giving a substantial LP? Should it be represented by a virtue? Should this virtue, in that case, be major?

It's. It that big of deal. An LR 14 isn't that hard to get, IMO.