I read with interest the comments and the 'devilish' solutions offered by many. No wonder HR is a hated term in organizations. Lack of job competency as well as sensitivity; though we pride ourselves as Human Resource Professionals. Ideally, we should be called In-human Treatment Professionals. The aim of every HR is to 'make life hell for every employee'. Sometimes I wonder if hell is full of HR persons, or the Devil is actually an HR guy in disguise.
Ever thought why Labor Courts favor the "labor"? Because it is an unequal fight. Management can fire thousands of employees and the next day find replacements, whereas a job is a source of livelihood for the whole family of the employee, and it takes considerable time to find another, during which, for the employee's family, many tragedies occur.
Now, coming to your problem, Ms. Swati; (Don't you think it is a greater problem for the employee?) Of course, you can fire the concerned employee after issuing a few notices of non-performance (just to appear FAIR in the eyes of Law).
But if you can take some pain, I suggest you STUDY her PERSONNEL FILE. Find out under what circumstances she was hired. Was she competent enough for the role for which she was hired? (If not, then is it really her fault?) How was her initial performance? Did you TRY to find out the ACTUAL CAUSE of her non-performance (informally or through COUNSELING)? Is it due to a BAD BOSS? Or, Bad colleagues bent on demoralizing their peers for their personal gains? Some family problem? Or, some change in TECHNOLOGY or PROCESS for which she is not equipped? etc. etc.
There are ways to solve some of these problems and to PROPEL the employee on the PATH OF PERFORMANCE. In fact, that is the PURPOSE of a good PERFORMANCE MANAGEMENT SYSTEM (and not to simply classify employees into a few pigeon-holes labeled A*, A B C, D, etc.).
If you can take the pains, please do the above.
If NOT, there are HUMANE WAYS of TERMINATING service. That is, you communicate to the employee in no uncertain terms about Management's agenda (while doing so, be as sensitive and empathetic as a good doctor conveying bad news to the patient or her family) and also offer support for her possible placement in another organization.
Not only will you be doing a good deed for the employee, her family, and society, but you'll also derive JOB SATISFACTION and pride for doing a good professional job.
Regards.