In Summer's younger days, she enrolled to Beacon Academy and became a member of Team STRQ, along with Taiyang Xiao Long, Raven Branwen, and Qrow Branwen. According to Taiyang, he, along with another unnamed member, played a prank on Qrow by telling him the skirt of the female uniforms was a kilt. By process of elimination, Summer most likely partook in the prank.
At some point later in life, Summer entered a relationship with Taiyang after Raven left, the two had their daughter, Ruby Rose, and Summer took to raising Yang Xiao Long as well. Summer's family lived in Patch as she left regularly to carry out missions. According to Yang, Summer was like a "supermom", doing activities such as baking cookies, and acting as a "slayer of monsters" due to her Huntress career.
It is revealed by Qrow that Summer acknowledged and utilized her abilities through her silver eyes. It is unknown when and how she discovered her abilities.
When Yang and Ruby were still young, Summer went on a mission and never came back. Specific details surrounding her fate are undisclosed or unknown. According to Yang, Ruby was too young to likely be able to fully comprehend what had happened.
Taiyang didn't handle the news nearly as well; Yang says he simply "shut down". It is after this that Yang learned Summer was the second love that he'd lost, the first being Yang's mother, which makes Summer Yang's stepmother.