This theory is probably pretty low on the totem pole of ideas, but we have to consider the idea that we're looking at this too deeply! Much like Sarah when she thinks there's some hidden lesson behind breaking out of the time loop — which leads to her "selfless" reveal to her sister, Tala (Camila Mendes), that she slept with her groom, Abe (Tyler Hoechlin), the night before the wedding — we could all be trying to assign a deeper meaning to the words of a sweet grandmother to her granddaughter.
Nana has obviously lived a couple of years, so of course, she's been to more weddings than Nyles or Sarah can imagine. Revealing the death of her mother is an obvious way to connect with her granddaughter, and when she bids Sarah good luck, it doesn't have to be more than that. Her farewell — "I guess you'll be going now. Good luck." — isn't an unbelievable thing to say when you come to the end of a conversation. It's actually pretty normal. So maybe Nana is the red herring to our Mystery Inc. gang and we've fallen for it, which is exactly what the cast and crew want us to do!
