As a Florida licensed attorney, I wanted to elaborate a little further on what the previous expert said. First, I agree 100% with his statement that a prosecutor is not likely to push a case with no evidence -they have far too many serious cases to waste time, so it is doubtful you have anything to worry about.
The previous expert is also correct in that even when a record is expunged, the record never truly dissa, though it can only be disclosed in very, very limited circumstances (such as where a person is applying for admission to the Florida Bar).
With respect to if your girlfriend did file a charge or you were arrested, there would be a record of this. Florida has a broad public records law. All arrest records and court
documents (unless sealed) are public records pursuant to chapter 119 of the Florida Statutes. A public record means that the documents comprising the record are open to public inspection by anyone. That also means an employer could
find the records in a background search if they searched court records (many don't). If the charges were dismissed, or no charges were filed, this would be reflected in the record -for instance "Arrest -no charges filed."