Rowena was driven out of her pack because she was sick with mange. Her pack did not have the cure for her illness, or the means for getting it, so they protected the rest of their cubs, and themselves by driving her out. Lei'luna is unwilling to leave any abandoned cub to their fates, so when Luna found her on one of her scouting trips, Lei'luna took her in. Ayla, the pack's herbalist had the cure she needed, and Rowena is fine now.
Rowena comes across as being arrogant, and even defiant at times. Part of that is a confidence in her own abilities, and a distrust in others after her own pack abandoned her for something that she couldn't help. And part of it is a mask to hide the fear that her new pack will abandon her too as soon as she gets sick again, or does something wrong.
She is a month and a half younger that Lyr and Thatcher, but she is determined to keep up with them in everything that they do.
Yuki was assigned as her pupsitter.