My cousin has struggled a lot with mental health, and I have supported her a lot over this for many years. My wedding is two weeks away, and she just texted me to say she is still unsure whether she and her partner will come because she is going through a difficult time. The partner will only come if she does. Is there a polite way of saying to her that it's fine not to come? It's not a big wedding and two people no-showing at the last minute will mess up table plans. The food is about fifty pounds a head and I need to confirm numbers with the caterer. I also just really really want to enjoy my wedding in an uncomplicated way - for various reasons I've been through a lot over the last few years. If cousin is upset at the wedding, I know she will cry on my mother and sister for most of the day (and possibly also me) and I really want them to enjoy it. I would genuinely love her to be there, but I'd also much rather just decide now that she isn't coming. We all support my cousin a lot the rest of the time.
I suppose YANBU is it's ok to tell her to skip plus here is a "polite way of telling her no"! and YABU is "let it play out and she'll come if she can".