Hi Neha,
Is the employee asking for relieving letter?
Relieving letter is very importanat in finding a job. If the employee wants to leave without a relieving letter, let her go. I am sure, her classmates would not follow the suit as they would need it for future jobs.
If she asks for a relieving letter, in full and final settlement, you can ask her to pay the bond amount. If she is not willing to go for final settlement, dont relieve her. Let her go if she wants without getting relieved...
Hope this will help a little.
Regards