Follow my weird mind:
As a waitress, Amanda Westfield worked for many people, for many billionaires in Star(ling) City. But, what if she worked from a distant father whose wife was killed by a thief and that his son was growing up alone... What if she worked for a man named Malcolm Merlyn?
She took care of Tommy and, eventually he and her child - whose father is her former boss, Justin Claybourne - Susan growned up together and formed a good friendship.
Eventually, Tommy died and The Hood killed Claybourne, and later, Malcolm became Ra's al Ghul and brought Tommy back. Tommy, who was feeling the blood lust, needed to kill Oliver, so he would feel better. But Malcolm, taking advantage from it, made Tommy believe that Oliver did something really bad to Tommy. Tommy was trained by Talia and, after that, returned to Star City, where he met with Susan, who wanted revenge against her father's dad. Tommy told her that The Hood, The Arrow and The Green Arrow are the same person and influenced her to get revenge for herself and for everyone whose justice was acting unfair
Before Malcolm traveled through time with Thawne and Darhk to face the Legends, he told Tommy everything that he knew about The Flash and The Legends.
Tommy became Prometheus and Susan, Vigilante.