With two young children and a smaller Yorkie in your home, you cannot take a chance on having an aggressive dog around.
Florida is a very pro-consumer state when it comes to pet laws. In addition, if the seller pulled a bait & switch on you, she could face serious serious charges.
If it's the same dog, the seller should refund your purchase price and take the dog back. You should be responsible for shipping costs.
If she switched dogs on you, you are entitled to the purchase price, shipping costs, and I would ask for reimbursement of vet bills. If you have to go to court, you would be entitled to court costs and attorney fees if applicable.
The dog needs to be returned before she does serious injury to your other dog or your children.