Thank you for the information and your question. Unless there was a statement in the divorce settlement/decree that said the debts and profits of the home would continue to be split 50/50, which doesn't sound like the case since there is now apparently one owner, then the current owner would be legally liable to pay the entire deposit back to the former tenant, regardless of how the deposit was split in the beginning.
The fact is, that under Florida law, the security deposit
was all supposed to go into a separate account for the benefit of the tenant anyway. In other words, it shouldn't have been split and used for anything else. You can see the statute that applies by going to: http://www.leg.state.fl.us/statutes/index.cfm?App_mode=Display_Statute&Search_String=&URL=0000-0099/0083/Sections/0083.49.html
As to whether a court would say that the other spouse (non-owner) must now produce half of the deposit to pay the owner who has the legal duty to pay it back, that is not likely. The owner can certainly go to small claims court and try to make their case, but if the home was jointly owned and now isn't and nothing in the divorce decree addressed the issue, they are going to just stick with the law, which is the owner must pay the security deposit with no contribution from the non-owner.
The only positive here for the owner, is that they may be able to take a deduction on their taxes if this is an actively managed property.