A single conviction of a misdemeanor shoplifting conviction would normally fall under the petty offense exception, so as not to prevent her from qualifying for a student visa. That does not necessarily mean that she'll get one -- just that she's unlikely to have been disqualified. She can consider applying for a F1 visa, to see what happens; if approval is very important to her, though, it would be sensible to speak with an immigration lawyer first, to discuss her situation in detail.