No one has yet responded to this part of your question, and I am going to surmise that she and/or her fiance is Catholic. It certainly would add complexity to the arrangements to try to find a RC Priest on island to perform a beach ceremony, especially by March 2016.

Another option would be to be married by at church by a Priest with a very small ceremony (just the couple and their witnesses) at some point before going to SXM where she can have her beach wedding without the hassle of all the legalities.

Just food for thought. I wish her the wedding she dreams of but more importantly a long and happy marriage.