My D is not inviting one of her aunts to her wedding. All other aunts and uncles are invited. The reason is that my half sister (who very likely has borderline personality disorder) is a toxic human being. She cares mainly about herself. She is extremely vicious if she feels even slightly rejected-and “rejected” could simply be someone disagreeing with her on any random issue, not responding quickly enough to a text, or not responding with the appropriate (by her definition) enthusiasm or tone. She has spent years sowing discontent in the family. Her life’s road is littered with the bodies of dead relationships. Her husband’s large family wants nothing to do with her and cut off all contact over a decade ago. She quit speaking to her mother’s whole side of the family after a public airing of family issues (complete with sister calling names and using profanity towards them on Facebook). I finally had enough last year and told her I didn’t wish ill on her but no longer wanted a relationship with her. After a minor disagreement, she had sent me a series of increasingly vicious emails that I finally quit reading after the first couple (total of 8 eventually). Later she wrote that she was willing to calmly discuss how I had sullied the relationship. I passed.
My life is immensely more peaceful and her presence is not missed one iota. D2 had been telling me for years that her aunt was a terrible human being and that I didn’t need to continue the relationship simply out of some sense of familial obligation, particularly since her aunt has shown a pattern of disregarding the importance of familial relationships herself. I finally got it.
D2 will have a lovely wedding surrounded only by people who care for her, her fiance, and each other. There will be no negativity, and that’s at least partly due to the fact that my sister will not be present. I doubt she will know about or even care about the wedding, but if she does find out about it and is insulted, I can’t be bothered enough to care.
As to OP-it’s hard to imagine omitting a beloved aunt from a wedding. Perhaps they are severely limited as it relates to guest list, and by omitting all aunts and uncles, they figure they can avoid hard feelings since none of them are coming and no one can claim favoritism. It does seem strange, though, particularly if this is a large wedding.
I can understand the hurt feelings. If OP still loves and cares for her niece and her sister, perhaps she can forgive and forget. If this is a reflection of a lifetime of toxicity, then it may well be time to re-evaluate the relationship.
I rarely advocate that family members break permanently from each other. But sometimes it’s the only way to reclaim one’s peace.