It's not really that far out there for Junna to move past the assault given a) it's in the past, on an alternate timeline even, b) Nana appears to hold deep regrets about it, and c) unlike the alternate timeline, Junna's up for it now, why let those events influence the current timeline.
Still, feels like some easy drama thrown in for the sake of drama. I'd prefer more fluffy Junna x Nana.
And reversals, I wouldn't mind some reversal.