Florida is not a common law marriage state. She might be able to sue him based on any number of equitable and contract theories such that they were joint partners in a venture, she unjustly enriched him, etc. But the law in Florida disfavors extensions such as those and instead favors people getting married. But I would need to know a lot more about the facts before I stated that she had no chance at all. Obviously she spent nearly 2 decades with him and that should be "worth" something one would think. Good luck.
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There is no common law marriage in FL so seeking any rights through that method will not work.
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