I was a bridesmaid for a wedding, and the bride's biological mother showed up uninvited 45min before the ceremony. They got into a screaming match, ending with the bride slapping her bio mom. Mom had the bride arrested.
Wedding ceremony didn't go on, but the reception did. When bio mom tried to crash that, cops were already in place to arrest her for trespass/DUI/public intox/public nuisance. Charges against the bride were dropped shortly after.
Bride and groom had a civil ceremony at the courthouse a couple weeks later, with just their immediate families present. (I had already deployed by then.)
Found out later on that the bride (who is VERY well off in her life, despite her trainwreck of a mother) secured a great civil attorney and successfully sued the woman for the embarrassment of the whole s**tshow and the cost of the wedding reception.
Mom had to sell her house (which she owned outright, as it had been given to her upon her parent's death) to cover the cost of the judgment, and later filed for bankruptcy. Insult to injury was finding out the bride would have let the whole thing go if mom agreed to go to rehab and therapy, but refused.