just a view catsinthejinglebelfry - that whatever some others have posted, you have every right to make your views known too, even if some vehemently deny them being acceptable (or to be clear, that they are "disrepectful" in the eyes of one particular poster, who elsewhere explicitly stated someone's views do not count - talk about live and let live - some might think she is leader of the Thought Police, to say what is and isn't allowed as views posted on a thread).
stoopidmistake - given the current situation your husband needs your support and attention and now you've had this 'scare' you know you won't be tempted to do anything similar.
FWIW, it's almost like a bunch of girls who change their "best friends" on a whim, and while it was flirting of a possibly intimate kind (ie not like flirting in full view at a party, and then just laughing it off later) the old friend is hardly going to give it a second try and you aren't either.
Just cross the bridge of explaining to your DH if there is contact from the 'other woman' and banish it from your head. If there have been financial and depression problems then your number one task is to see things past Christmas and New Year as those can be stressful times anyway... Wishing you the best of luck, and don't expect the worst to happen - you have already turned a corner, closed that online flirting door behind you, and need to look forwards to happier times for yourself and DH.
(Unsure, if he has moved out, why he cannot explain fully to you what has happened, and how much 'she' knows about you - I guess he may have an e-mail address or some forum 'username' for how he has been in touch with you and perhaps there's still a PC in her control so contact would be dumb.)