In one of the timelines Nadia's mother didn't die
They have to find some source of drama for a second season, and this seems like a fairly obvious thing to do, particularly given the lack of closure about how she actually died and the centrality of her death to... whatever is causing the loop thing (the fact it happens on Nadia's 36th birthday, the inner child thing, the focus on deaths in general). Nadia's mother was, or perhaps still is, caught in another, possibly much longer, loop.
This led to her mental decline as she tried to break it. As a corollary to the above, Nadia may be right about loops continuing even after they die.
The Nadia we know may exist in one such loop, seeing as her mother has already passed. The first loop we see isn't really the first loop.
This is why Nadia recognizes Horse even though she hasn't met him yet.Nadia is in The Bad Place
Or the new Good Place, since the timeloops teach her to be a better person so she can get into the good place.