Lying about being married is crazy. The chance of that working is virtually nil.
The OP was hoping to fade but has been caught out doing something that will get her DFed. Without wishing to sound harsh, if she wanted a quiet fade then moving in with her boyfriend within a few months of stopping meeting attendance was always a big risk.
Sending lawyer letters is all well and good but unlikely to prevent the same basic outcome.
Either way if she wants to try and maintain key personal relationships (e..g. with her mother) then the real power lies with those ones. Even if she is successful in preventing a formal announcement, her mother and others know her true situation and it's their decision about how far they go in the range of loyalty to the org or loyalty to their family and friend.
IMHO the OP has made her choice by taking the step of moving in with her boyfriend. I would encourage her to think positively about the future, hold her head up high, ignore the elders and focus emotional time and energy on her relationship with her mother rather than playing silly games with people in an organisation she no longer wishes to be part of.