Employment Law Questions? Ask an Employment Lawyer.
Job abandonment, is anything the company decides they want it to be. Some businesses might say "no call, no show' for 3 days means the person has given up the job, some might say only 2. It is just a term people use, and if you are the business owner, you can assume anytime you want that a person has abandoned the job. In your case, you will have to change the locks and take security steps to make certain she cannot access anything in the business.
You have the right to hire and fire at will, unless there is some contract which would protect this employee and let her miss this amount of work. I doubt this is true, so you are completely in the right if you fire her.