[@Sep] Yeah the Flash continuity is all kinds of effed up, even more than other comics can be, and I think we're better off streamlining a lot of it. But Malcolm Thawne had other relatives, and its not unlikely that one would have met Don Allen at some point if many of the Thawnes pursued a criminal lifestyle. Perhaps one met Don and reformed. This prospective relation might also be Owen Mercer's mother as well, perhaps from her past criminal life where she would have met Boomerang. So similar to the continuity but without all of the timeline hi-jinks. 

That's just my idea, what do you think?