The girls saw Daimon returning alone and they were naturally curious about what happened, especially Cassy who seemed to be worried about Jasmine.
Cassy was older than Jasmine and technically the tree of them became friends at the same time, Sylvie didn't marry nor had children unlike Jessica and Bell, so she didn't have a daughter that could get along with Jasmine.
But Underwood's wife was also Aurora's disciple, despite the fact that she isn't a light affinity user, so it was natural for the little girls to meet and get along.
Cassy didn't know Sarah's backstory but she one day just suddenly distanced herself from them, and then started avoiding them and just observing from afar, Jasmine might not remember but she does.
