My tenant was scheduled to move in today and last night she notified me via text that she wanted her security deposit back and that she was not moving. She said it was because her allergies were acting up due to our animals that were no longer in the house. These animals were in the house the three times she was there previously for 10 to 15 minutes with each visit. Which means they were there when we signed the lease. I told her I would have the house and carpets professionally cleaned prior to her move in, which I did. I also agreed (last night) to have a two day pet enzyme carpet treatment completed again, which was started this morning by the carpet cleaner. She would be able to move in Sunday afternoon. I never deposited her prorated rent check, so I returned that to her, but I told her she would not get her deposit back. My question is, do I owe her the deposit since she broke the lease without cause?

If the lease was signed and money paid, you do not have to return anything and she is liable for all rent payments till you find a new tenant. She owes you what the lease ( contract) that was signed says she owes for breaking the lease.

"scheduled to move in today and last night she notified " did she have a signed lease, when was it scheduled to end. Did either of you give each other notice in the proper time frame?

She signed a 24 month lease on March 29th and she was due to take possession of the property today. I did not receive formal notice, just notice by text last evening, that she wanted her deposit back and she would not be moving in.

Where is the unit located? In most places you not only do not have to give the deposit back, you can keep charging rent until you find a new tenant. Chuck already mentioned this and he is correct. If she refuses then you could sue her for your losses. Did the lease have any wording about early termination or notice?

It is located in Florida. We had an early termination fee/liquidated damages addendum that we both signed. We checked the box that said, "I do not agree to liquidated damages or an early termination fee, and I acknowledge that the landlord may seek damages as provided by law."

And Florida law is on your side here. Unlike most other states Fl does not require that you make a good faith effort to find a new tenant.

In fact you made a mistake by giving her back the rent check. She can use that to say you released her.

So I would go about finding a replacement, when one moves in you send her a bill for the rent you lost up to the time the new tennat moved in, minus the amount of the deposit. Tell her if she doesn't pay you will take her to court. Then do so.