she refuses to take it in baldur's gate... unsure how you got her to take it.
You can't. AFAIK, the only shroom you can give to her to unlock a memory is the one you pick up in the Underdark.
From all I know from my own play-throughs and from what other players reported:
There is at least one more Noblestalk in Act III, but it doesn't have the same special "story-properties" as the one you pick up in the Underdark. You can consume it to heal a character, you can sell it, but you can't give it to SH and you can't give it to the Dwarf-lady to fulfill her original Noblestalk quest. I let SH pick it up, picked it up myself and then started a conversation with her, I had it on my Tav when talking to the Dwarf-lady in her store and I even sold it to her, hoping that would fix her store's money problems. None of it worked.
I always feed it to SH while in the Underdark, because... of course, so I can't verify this, but: I *think* not giving the Dwarf the shroom in the Underdark results in her store being a bit underwhelming once you get to Act III.
For one thing: She more or less tells you so and blames Tav for her lack of customers. Plus she's always broke when I visit her after a long rest. Like 10 or 15 GP when other stores have at least 1000 to 2000 GP on hand and some even have 10000 or more.
S.