J.K.
It sounds like she's just trying to have the discussion as its unlikely that legally she could just up and move with him. Review the decree though as not everyone has restrictions on moving. I, myself, am the school placement parent so I could move and my children would attend school wherever I live.
Don't go into the meeting with guns blazing but be open to the discussion. Yes, there is what you can legally do, but it sounds like you'd like a resolution rather than forcing the "legal" part.
Talk to her about moving closer to you and job opportunities as you seem to have first-hand knowledge on that. I would even offer the additional money to have them living in Naples as that sounds like it would really be the best option for all of you and it would be offset by not driving or potentially flying. That would put him in the same community and afford you the option of attending games, conferences, doing sleepovers, etc. and truly sharing more time with him. Especially with his mothers issues, you would be right there to observe and step in at a moment's notice.