A similar entry appears in the Wheel of Time Companion confirming the information available in the main story arc.
Author: Atarah al'Norahn
Anghara was an ancient Amyrlin Seat. Mat has memories of Isebele of Dal Calain making Anghara come to her instead of the other way around. Mat knows that this is an old memory, because apparently Dal Calain disappeared during the Trolloc Wars (ACoS, Ch. 16).
Although the above information comes directly from the books, the fact that Dal Calain is connected to the Trolloc Wars is somewhat confusing. Mat thinks to himself that "Dal Calain had vanished in the Trolloc Wars" (ACoS, Ch. 16), when in fact, according to "The World of Robert Jordan's "The Wheel of Time", Dal Calain was one of the nations of the Free Era, which took place after the Trolloc Wars. So, if Anghara is connected to Isebele of Dal Calain, it can be surmised that she lived during the Free Era, although the books seem to say that she lived either before or during the Trolloc Wars. Perhaps it was supposed to say that Dal Calain vanished during the War of the Hundred Years. It is most likely just a simple mistake.