Good question. The law says that moving an object, even within a store, with the intent to steal it, is stealing. The issue then becomes what evidence there was that she intended to steal it. If a person hides an item in their underwear, pretty good indication they intend to steal it. If they put it in their purse? Less clear, but probably good enough for most juries.
Evidence that she paid for some items, while she failed to pay for other items in her purse, is strong evidence of an intent to shoplift. In addition, her statement that that was her intention will be admissible against her, even if she was scared when she made it. What is her innocent explanation of why some items were in her cart and others in her purse? The question is whether a jury will be satisfied beyond a reasonable doubt that she intended to steal. Here, the evidence is more than sufficient. It is possible, as you point out, that she planned to go to a different cashier and pay for the items in her purse, just as it is possible she could have been struck by lightning as she walked to her car. Possible, just extremely unlikely.
This answer is provided for educational purposes only and is not intended as the practice of law in any jurisdiction in which I am not licensed. The answer does not constitute legal advice nor does it create an attorney-client relationship. The answer is based only on the information provided, and may be inaccurate in the context of additional facts that have not been provided. The questioner should be aware that I am only licensed to practice law in the state and federal courts of Minnesota. Accordingly, before taking any action or refraining from taking any action, the questioner should consult with an attorney licensed to practice in his or her jurisdiction.
Leaving the store isn't a prerequisite for a shoplifting charge. I think she should get a lawyer to defend her, s/he may be able to negotiate a favorable disposition for her as well.
THESE CASES ARE ALL ABOUT NEGOTIATING A GOOD RESOLUTION FOR A DEFERRED ENTRY OF JUDGMENT, CIVIL COMPROMISE, OR REDUCTION TO AN INFRACTION.
WHEN IS HER COURT DATE?