Wow, she really needs a life. I wonder how her new husband would feel about this.
I totally agree with LadyP. He needs to be the one to put his foot down and put up some boundaries.
There was really NO need for her to call today, she could have sent a second email saying that it was not meant for him. Your FI needs to tell her to ONLY call if it involves his son and thats it.
Steve had some issues with his ex when their divorce was a little more fresh, but he put his foot down and she no longer calls on his cell phone unless its an emergency and only calls him at work if it's about their son.
I hope she gets a life and starts respecting you and him soon.