It does look like a South Sea pearl necklace...but can't be 100% sure just by looking at the photos. What strikes me odd: a silver clasp on a SSP necklace.
The pearls look like Akoya and the clasp has the Mikimoto logo...the style of necklace is not very common, yet not rare....can't recall how its called.
It looks beautiful, very well matched and arranged.
Well, at first sight they seem to be Potatoe freshwater pearls from China...but they could also be natural baroque pearls.
Did she leave any information about the pearls? Source/origin?