I could swear I just had this sentence a few questions back and feirmeoirí was eclipsed...?
It might have been. That error has happened a few times (eclipse after plural article) though it shouldn't.
Why is 'isti' as 'aisti'?
There is no such word as isti.
asam, asat, as, aisti, asainn, asaibh, astu.
Well, when you click on the hint it tells you that "in her" is isti. Reported, but I feel like this unit in particular is bad with a lot of the "in x" hints.
Isnt "aisti" from her and "inti" in her ?
aisti is the 3rd person singular feminine prepositional pronoun form of as. inti is the 3rd person singular feminine prepositional pronoun form of i.
In Irish, the preposition as is used with muinín to indicate the object of that trust.