Assuming there are no restrictions on your right of visitation, I’d say that your ex’s position is not legit. However, if she refuses to let your current significant other see the child, you could be stuck. Find out from the police department in the town where your ex is living whether they intervene in these situations and the type of proof that they might require to enforce visitation. If they do intervene, make sure you get a certified copy of your visitation agreement that shows that you have visitation rights.
After watching the video:
The other alternative is to file a Motion for Order with the court (you can do this pro se) asking the judge to prohibit your ex from interfering with the visitation (the downside being that you probably have to appear in the Florida court). Do this well in advance of the visitation to give the judge time to issue the order.