Hi Bharat,
If I'm not mistaken, what Maithili requires is a formal request letter to her employer for the issuance of a salary certificate. It seems she is currently employed but has not been provided with any pay slips, especially those indicating cash payments, etc. This certificate would be for her future reference and for use when she decides to leave her current job. If this understanding is accurate, a suitable format can be shared.
Please let me know if any additional information is needed.
Thank you.