Your attorney in Miami should know that they can always ask the court for permission for the witness to appear by video or by telephone. It isn't the best solution, but it is an option. And if all else fails, the witness can always submit a signed declaration, though of course that is not the best evidence because the other side doesn't get to cross-examine the witness, but something is better than nothing. As to getting her to come over the U.S., it is possible, but not easy. She would have to apply for a regular B1/B2 visitor visa and show non-immigrant intent and strong ties to her home.
You can look at the link below for all the information that you need on the visitor visa:
Essentially, she must have a valid reason for visiting, must have a way to support herself without working illegally, must have significant ties to her home country, and must have the intent to return home.
Though I doubt they would approve it for a civil case, she could also try a Humanitarian Parole. Here is a link:
Hopefully she can show enough strong ties to Cuba and non-immigrant intent to be able to get the B1/B2.
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