You can't sue people for being rude. Rude behavior is not actionable unless it is also unlawful.
As a matter of general law, shopkeepers can investigate whether someone is stealing from their premises. Sometimes they are going to be right, and sometimes they are going to be wrong.
Could this employee have asked you politely? Certainly. Did she do anything that gives you the right to sue her or her employer? No. Did she defame you? No. She asked you if you paid for the drink in your purse. She's entitled to ask you that.
Not legal advice as I don't practice law in Tennessee. It's just my two cents on the facts you present in light of general principles of law. If you need legal advice, please consult a lawyer who holds Tennessee licensure.