Is there reason to fear a lawsuit from an employee who egregiously violates our policy?

Q. We just hired a new M.A. and found out on her first week of employment that she was a registered nurse and her license has been suspended. She was let go from her last job. She did not tell us this, and of course we did not ask. Our manual states dishonesty and also drug use as criteria for firing. Her license was suspended for possession of drugs (marijuana). Part of her probation mandates that she cannot practice nursing until licensed by the N.C. Board of Nursing for 24 months. Based on this information, is it "safe" to let her go immediately or are we setting ourselves up for a lawsuit? – Joyce, North Carolina