You are very welcome. :)
If Florida operates similarly to my state, the Courts will take over the monitoring of your mother's accounts through the reports provided by the one who is listed as the "Guardian of the Estate" or "Conservator." It appears that you have served unofficially as the "Guardian of her Person." These terms are best described at a senior care site I found (http://www.parentgiving.com/elder-care/guardianship-versus-conservatorship-what-is-the-difference/ ). Your POA is nothing compared to the title of "Guardian of an Estate." Depending on her cognitive state, you may be asking for both.
Cagefigher is right in that in dealing with the Courts and the attorneys you want to be brief but direct. Here's your line... ready?
To the Courts (in person where they can hand you paperwork that may lead to less legal fees):
"My mother has been living with me for X years. I have two sisters who have taken control of her finances but somehow, my mom and I see very little of this money. I have concerns about where much of this money has gone, but, most importantly, to care for her properly, I believe I need to see about becoming the Guardian of her Estate. How do I go about doing this? What paperwork do I need to file? Can I get the paperwork here at the Courts?"
That's it. Shut up... listen and learn. Your goal is to understand the process.
What's the most valuable education? I checked and it appears that proceedings in Florida are open to the public. Call and explain to court staff that you're really nervous about what you're about to go through, find out when guardianship matters are scheduled and GO AND WATCH A FEW. You'll see how an attorney will help you present the facts of the case with keywords the Court.... shall we say... will understand. You'll also see that the Courts will not have time to care about personal emotional testimonies.
Then, once the process is clear, to the attorney:
"Hi, my name is XXXXX. My mother has been living with me for X years. I have two sisters who have taken control of her finances but somehow, my mom and I see very little of this money. I have POA and I have concerns about where much of this money has gone , but, most importantly, to care for her properly, I believe I need to see about becoming the Guardian of her Estate. I've completed many of the Court required forms. Can your firm help me?"
Going to Court will be an emotional challenge because this is very personal to you but this is routine Court work. The courts have much more experience with "where'd the money go" challenges than you do. They've seen people who are much more savvy than your JW sisters. Please remember, the Courts see people who are only interested in the financial welfare of a person's challenges but not their personal welfare ALL THE TIME. They will read through your sister's motivations VERY quickly. Be psychologically prepared for your sisters' anger to change direction REALLY fast to a "how could you do this to us???" mentality. They will use psychological warfare that will include your perceived desire to hurt the family. IGNORE IT. They will become the victims and they'll swear your mother, who is in your care, is somehow a victim of your actions as well. RELAX, the Courts have seen that too. Your sisters will have a tough time making the Courts understand why they left their poor mother in your care for years.
The freedom you'll feel when you can say, "Sorry, the Courts made the decision, not me" will be liberating.
Unless there's a piece I'm not aware of, I suspect much will go your way. :)