I’m sure her sister is just mostly concerned about her sister, no matter how close they may or may not be she would probably swap her day for her sisters health. She seems like a nice person from what little we have seen. She probably just wants her sister to enjoy the day and has assigned duties to other bridesmaids etc. As much as Nicky annoys me I doubt very much that she wants to ruin her sisters day or take centre stage. If that’s her intention then I feel sorry for her
Yes, it is a very painful circumstance for all. I honestly don't know how I'd deal with it if I'd planned my approaching nuptials, yet my sister was doing so poorly, yet in a non-linear and unpredictable pattern as the big day approached. Depending upon how NNL is really doing, I may be inclined to hold a private ceremony ASAP, with my sister in attendance, then carry on with the planned wedding which would take any pressure off if she could or could not attend, but perhaps have a livestream available for her to view it, if she was unable. That could allay any demands or responsibilities or stress about it and yet still include her and have her be a part of such an important life event no matter how the next few weeks unfold.
For me, the dichotomy between NNL making funeral prep at the same time as her sister's momentous imminent life event remains very stark. I don't know how to reconcile or compartmentalise those two opposing trajectories that are occurring at the same time within one family. Very sad.