Publicly, they were best friends while both studied in Sharlayan, as denoted by their dialogues and Urianger's conversation with her parents. Secretively, I and the fandom suspect there were more than meets the eye in their relationship. One, due to Moenbryda's constant nagging and flirting with Urianger. Two, because of her minion's former description. Well, they were practically in college, so booty calls were expected.