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The short answer to your question comes down to the "status" of the child in the eyes of the USCIS. Did you obtain legal guardianship over the child? How did the placement of her in your home occur, and through what visa process?
In Florida, you would not need a home study for a step-parent adoption. You would have to check the Adoption Statute of your home state. If a home study is required, you should have it done before filing your petition for adoption.