I mean, it's Eternal return, more than likely she IS that previous incarnation from the previous universe. They're the same cycle.
We also have this reality's Mokou and presumably Kaguya who are literally the same individuals from cycle to cycle after the one where they drank the elixir unless they managed to somehow pass on courtesy of the SDM, with only sheer time scraping away their memories.
On the other hand, something is giving this Remilia melancholic deja vu. What that is has got to be significant.
It's a bit sad that Patchy just leaves, she probably dies too but it's still depressing that she wasn't there for the other's final moments and for them to see her final moments