The Multiple Solution

Her last summer home, Harriet Potter escapes Privet Drive by pulling Hermes' memory trick on the Dursleys and sending them to America, spending the rest of the summer with Hermes at his empty house. Dumbledore is reluctantly impressed by this tactic and reveals his plan to win the war: a ritual to summon six other Harriet Potters from other worlds to help them. Too bad Harriet's counterparts are already wary of him and his noble cause.

Or, a mostly-canon Harriet meets her counterparts from my other crossover stories.
Young characters + Remadora genderswapped, everyone else the same.
Warning: This is a crack teaser!