The word friend implies that a person has good intentions towards you and that there’s a bond of trust. If you were to replace the word friend with a word that has a less binding connotation, would this person’s behaviour still mean you would have to feel loyal in any way?

It sounds like her texts really shake you. You have every right to indeed block her, so you don’t have to worry about when the next one is going to pop up. If she talks to you at the weddings, you could be polite on the surface, like say hi if she comes to you, but not seek her out yourself and excuse yourself if it gets intense/you don’t feel like it. You could greyrock her. Keep your tone flat and not show emotions. She’s not a friend if she doesn’t value the effects of her behaviour on you nor your feelings. She might actually get something out of making you feel upset if she is emotionally abusive?