I'm Lucy, and I'd be happy to answer your questions today. I'm sorry to hear that this happened.
Legally, you're all equal owners with equal rights to the property. That means if all 5 of you decided you wanted to move in, it would be up to the 5 of you to work it out. She can't make you leave, as partial owner, and you can't make her leave. The only exception would be if your father's will had created a schedule for who could use the property when or if all five of you had a written enforceable agreement.
What you can do is bring a lawsuit asking a judge to order her to buy your share at the fair market value. This is what happens when joint owners of real estate cannot decide on how it should be used. If all of your other siblings agree with you, then the four of you can sue her together, and she can be required to buy out ALL of your interests. If she can't afford it, the judge will order that the house be sold at market value to a third party and the proceeds split 5 ways. If the new owner isn't interested in a tenant, your sister will have to leave at that point. This is called Partition by Sale, and any local attorney can help you set it up.
If you'd prefer not to go to court, the other option is to ask a local attorney in Florida to send her a letter, giving her the chance to either share the property, buy you all out, or work with the rest of you to hire a Realtor, or you'll go to court. You can write the letter yourself, but she might give it more attention from a lawyer. If you prefer not to pay someone else to write it, sending it via certified mail and giving her a firm deadline to send you her decision in writing can help her understand that you're serious about this.
You may also be able to sue her for the share of expenses all of you have been putting in since she started depriving you of the use and benefit of the property. She's enriching herself at your expense by allowing you to pay 1/5 of the fees each, but not allowing you to get any benefit from the property.
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