It wouldn't be the first time that Usagi's met people from TBH. She was a lot older then, at least her mid-late twenties? Again IDK vague backstory so if we go this route we can just go "OH HAY DEJAVU" and leave it at that. or we could just head canon a whole bunch of stuff for the hell of it because WHY NOT it's an AU.

Sword ghost is fine by Usagi's books. SHE CAN HANDLE MOST ANYTHING BUT GENGARS AND DRIFLOONS. IT SHALL BE SO. USAGI WILL MAKE ICHIGO FEEL LIKE A NORMAL GUY. IT'S IN HER CHARACTER TROPE... I MEAN IT'S WHAT SHE DOES.