I'd have to research FL law but this lady doesn't even stay there 7 days a week. She does not contribute to rent, have utilities in her name, her driver's license is an address 15 minutes away, she doesn't get mail there, and she has other places to go. Typically you have to have something to establish that you are more than an unwelcome guest (and most Google searches on unwanted guests when you read the story the person has been there months and months, gets mail there, contributes something to the household and really are more than unwanted guests).
Regardless, you may be right. However, I'd still call the cops and I think this situation is a lot different than most in that this woman isn't even living there all week. She's got two or three places she's going between and with that I think the OP and her mom have more rights than a guest who has moved in and has made the place their primary residency.