She first appeared in Young Avengers #1 (April, 2005). The issue was scripted by Allan Heinberg and drawn by Jim Cheung.
Fictional character biography
Young Avengers Special
Young Avengers Special revealed that sometime prior to joining the team she was brutally attacked in (what appears to be) Central Park. At first, the incident left Kate traumatized, but then it spurred her to engage in intense combat training. So far the team is unaware of this incident as Kate only told her therapist and Jessica Jones. The exact nature of the attack is not made clear—only the initial ambush is shown on panel. However, based on her conversation with Jessica Jones, it can be assumed that the attack was sexual in nature – most likely rape – since Jessica Jones replies that a similar incident led her to end her own superhero career (a reference to the psychological sexual torture she went through for eight months at the hands of Zebediah Killgrave).