Really? File "follow to join" for the husband?
Admittedly no one here is claiming to be an immigration lawyer or an expert in US immigration laws but I think it is very important for us to have a decent understanding of the process (at least) before we start throwing legalistic jargons around.
This woman's case does not qualify for a 'follow to join' process. IMO, there's no point giving her false hopes. Yes she can continue processing as "single" since that is what she played the lottery as, while technically she was still married. She will basically have to forget about this marriage if she wants to proceed with the selection. However, she will live in fear of potential discovery, her GC can be withdrawn if she's found to have fraudulently gotten it by withholding material information. If it's discovered after she becomes a USC, the citizenship can be revoked, she will face criminal charges which will most likely be followed with deportation and a life time ban!
Britsimon's response is a sound one, harsh as it may look. While being selected could be seen as a 'life time opportunity' living in the US is not a do or die affair! This lady is setting herself up for the possibility of being charged with a criminal offense by stating on the DS form that she is single when she clearly isn't! The DS form clearly states providing false information on the form could result in criminal charges being filed. However, not showing up for the interview could be interpreted as withdrawing the information since the form hasn't been signed.
There are numerous cases if people who fraudulently obtained the GC and were discovered numerous years later. I'm sure a google search will bring up some of those cases. As a matter of fact, Makiki did post on the 2013 Kenyan thread of a man who who did not include his son during his initial processing, after obtaining his GC he tried to bring his son to the US, of course he was discovered and prevented from returning.
Partitas, I'm implore you to present all the responses generated to this lady and she can go ahead and make her own decision.