Who is Jessamine from The Warrior Heir and what is their importance?

Jessamine Longbranch is the Procurer of Warriors. She works for the White Rose, as the premier wizard of the White Rose. Jessamine is also a healer and well known heart surgeon. When Jack was a baby, she implanted a warrior's stone instead of his rightful Wizard's stone, and she continues to monitor his health once or twice a year.