Humm heres a ideal how they get into the mess of being hurtled through various dimensions/realitys is do to whoever called the trouble(Maybe for simplicity use Klarion that) hadn't thought of protecting the item that allows the separation from mundane weaponry(you know stuff most DC villains and Hero's don't use) and other mundane items which Harley had used something on it that caused the item to either break into pieces,crack or malfunction so back it does the hurtling thing.
Humm it'd be kinda funny in my mind if Harley at a point ends up in Batman Beyond timeline where she ends up having 'fun' with some of that timestreams version of hers descendants after they insult her for being dressed like a baby or little girl maybe Harleys even in a rather full diaper at the time aswell Anyway heres a image of what I mean by 'fun'
http://bladevstwilight.deviantart.co...wins-597600324