My understanding is that Auntie Ethyl is the primary source of Potion of Hill Giant Strength in game. It is unclear to me whether the potion can be obtained from her after certain events take place.

("SPOILER")
My understanding is that the party may confront Ethyl at the end of Act 1. The party can fight her, in which case she is killed or can be allowed to live and keep Mayrina in exchange for her hair. Alternately, the party can deceive Ethyl into thinking they will assist her in conducting her ritual but then betray her, in which case she will drop her hair and run away.

Following these events,

("SPOILER")
if Ethyl is still alive, can she be found in game, and will she sell the potion?


Otherwise, are there other vendors who sell the potion on a continuing basis?