If I bought an apartment prior to getting married but my wife and I never lived in it so we rented it out, does she have any rights to it?

Generally, property obtained prior to marriage will be considered your separate property, even in Florida.  However, if you add her name to the property or you gift your wife a portion of the interest in the apartment, you could change the nature and character of the property-- and thus her rights to it.  To keep the title clear, keep it in your name only.  I would recommend the same for anything connected to the apartment like taxes or dues-- if you are going to payment (instead of a rentor), then have the account in your name only.

If the apartment has been generating income, there is a potential that she could be entitled to a portion of the income from the apartment, but not the apartment itself.  This means that if you put the rental income into a specific account, she could make a claim for a portion of the proceeds that are still available in that account.  If the proceeds are no longer available because you used the rental proceeds to pay for other things, then you are not required to go pay her back for funds that have already been expended.

With all that being said, she doesn't have any rights to your apartment right now.  If something happened during a divorce action, then a judge could potentially award her a judgment against your apartment if there were issues regarding your conduct during the marriage.  Just to give you a peace of mind, consider visiting with a family law attorney to know what issues trigger the judges in your jurisdiction to do this, if at all.  For example, some judges used to really get offended at the idea of adultery... however, with the influx of adultery cases in the judicial system, judges have become desensitized to adultery issues and don't penalize like they used to.  The only way to know what is offensive to your local judges is to visit with an attorney or two who regularly practices in your jurisdictions family courts.