She had hard eyes. She was lean and the same height as Egwene al'Vere.
Berisha was a strong sister in the One Power. It can be guessed for two reasons: firstly Berisha did not defer to Katerine, who is known to be strong in the One Power; the second is that Berisha alone opened a gateway large enough for a cart to pass trough (for a female channeler in the Aes Sedai ranks this power is even too much). The WOT Companion is silent on her actual strength level.
She was from Arafel. She stood high in the Aes Sedai hierarchy.
She had a reputation for the strictest, and often harshest, interpretation of the law. She adhered to the letter of the law, with no sense of mercy.
She said that Egwene's judgement would require the use of a High Court, with the Hall sitting to deliberate on the verdict. Katerine Alruddin suggested that Berisha might be called on to act as the Chair of Pardon. This role is one that Berisha certainly didn't relish, especially since the Chair sometimes shared the same fate as her defendant.
She chastised Katerine for scaring Nicola Treehill by saying that novices should be guided and not bludgeoned.
Katerine and Barasine made implied threats towards Berisha and Berisha left Egwene in their custody. Egwene thought that no woman who gave into fear so easily could ever have obtained the shawl and that something must have been very wrong.
During the initial days of the Last Battle, Egwene, as the new Amyrlin Seat, had Faile go to the Tower and recover the Horn of Valere. Berisha was ready to open a gateway for her, transporting the Horn hidden among other goods in a cart to the Field of Merrilor. In that moment the convoy was surprised by a bubble of evil which hurt Berisha in the foot, this might have caused the gateway to open wrongly, leading the group into the Blight instead. Shortly afterwards, Berisha was stabbed to death by Aravine, a Darkfriend who wanted to erase any sign of Faile and her expedition.