Dear Sir,
first of all don need to be get so upset. well first of all no need to send any polite legal notice or any notice
to her. once clear with your thoughts what do you want to do. because in my point of view if your wife is threatening you that she file 406/498 she is separated from you from past 4 months so if she wants to do she needs to be stay with you and but as she is separated so how can she blame you.
i will advice you to go to the local police station and meet with your area concerned S.S.P or local commissioner of police and write an complaint that your wife is threatening you. then next step is involve his family ask first them to get divorce with mutual consent. you can also file an complaint in magistrate court about wrong allegations that your wife is claiming on you and she is blackmailing you.
no need to Cary this kind of relation where she is not trusting you and not respecting this relationship.
if you want to reply by para wise just email me that notice which your advocate sent to her.
and lastly no need to file RCA because if any chance she file any case anticipatory bail can be filed.
first you just contact her family members ask them what they want. and inform all these allegations are not true and she is harassing you and blackmailing you.
if you need any more advice you can can ask me anytime.
regards
SAPNA SETH
Advocate