I rent a Esthetician room in Florida for $800 per month. After paying the full rent of $800 (it's written on my check rent for 5/6-6/6) due to financial difficulties I decided on the 17th to remove my belongings. The salon owner is refusing to reimburse me the rent for the remaining of the month and already has another Esthetician working out of the room. There is no contract involved, we've only made a verbal agreement regarding what day to pay the rent. Does she have the right not to reimburse me for the remaining days I'm not occupying the room?

If you didn't give her due notice then I guess she is entitled not to reimburse you. Or, basically, why did you send another month's rent ?

I told her I would stay until the end of the month if she needed me too, however she declined and already has another Esthetician in the room renting it. I was told to come pick up the check yet when I showed up her story was after talking to her boyfriend she thinks differently. (her boyfriend is 20% owner)

You were not smart to make a business transaction without anything in writing. This is not a real estate issue but a business issue.

If she refuses to reimburse you from the time she re-rented the space, you will have to take her to court for that amount. Your chances in court are iffy.
Without anything in writing, it's a general business practice to give notice equal to one full rental period. However, she shouldn't be allowed to double dip if she already rented the room. Whether a judge decides one way or the other is a tossup. If it were me I would side with her as a lesson to you to get everything in writing.

I would say that you have paid for the room until June 6 whether you use it or not.

You can't get your money back but you can charge whoever is using it for the remainder or use it yourself for the remainder of the elapse time.