Possibly a personality disorder such as borderline or narcissism. A narcissist would be jealous of their son's wife because she would see the son as valuable purely as an attention source: the son's wife is seen as competition/attention thief, additionally a constant reminder that the mother is not the center of the son's world.
If this is the case, it's extremely likely that the mother kicked up a massive amount of drama at the wedding. In her mind, her need for attention would be more important than her son's wedding. She would play tricks like interfere with the wedding plans, create some scenario where she is the victim, or, create a drama where the wife or wife's family is "bad".
The problem with pathological narcissism is that the narcissist doesn't have enough insight to recognize that they have a disorder and seek out healing; it's widely believed that it is not possible to "cure" a narcissist, and so many therapists refuse to take them as patients. For the family of the narcissist, if the disorder is bad enough that it results in extreme stress or mental/emotional health problems in the family, it boils down to: keeping distance, and defining hard boundaries. eg. "Mom, you will call us the day before visiting to arrange a time that works for us, not just show up on the doorstep." If this strategy is not successful, unfortunately the only remaining option is to cut them out of your life. This sounds harsh and will make no sense to people who have not truly experienced first hand the destructiveness, manipulative potential, and crazy making of a full blown narcissist, and in fact to the casual outside observer, the narcissist may well appear to be a very charismatic, well balanced, hard working and even successful member of the community. Narcissists may seek out positions of trust and power: politician, teacher, priest, police officer specifically in order to exploit that trust.
Narcissists are not capable of love as normal people would understand it.
If you have a narcissist in your family, I'm sorry for your loss. There is no chance of having a normal family relationship with this person, and as long as you believe there is a chance, they will use it against you.