I would say it's pretty premature to announce you're in a new relationship before you have official separated. That is, of course, my own opinion, but after all, that's all we're offering here.
Marriage is a social construct. Facebook is a social media platform. Publicizing your new boyfriend before you've started the process of legally ending your marriage is not socially acceptable, at least where I am.
I'm not sure how anyone not close to them would know that though. Some separations are just 'breaks' while the couple evaluates their personal feelings on whether or not to continue or end a marriage. Others are just the first step to divorce. I also believe that 'legal' separations, in some states, are just as complicated as divorces with separating assets, child custody arrangements, filing court documents, etc, so many couples choose not to go that route and just separate and file for divorce.
The legal issue is different than the social one. Publicizing a new relationship
, while not yet fully divorced, (with or without FB) may very well be socially unacceptable in many circles and I think it's perfectly ok for her to feel the social consequences of that behavior.
If you don't personally agree with it, then it's fine to back off the friendship.
That does not mean however, that your particular view, or that of your social circle is universal. It also does not mean that she is wrong for how she chooses to move on or what her timeline is...and this even if her STBX doesn't agree or like it. Every relationship
is different and I don't care how close you are to one or both members of a couple, I think it's pretty much impossible to understand all the in and outs of their relationship
We can choose to dissaciate with those we diapprove of, but I don't think we can say "this is the only way you are allowed to behave" and expect them to change to please us. While I personally have strong feelings about when it would be ok to start a new relationship
after an old one has ended, I don't think it's my place to expect or demand that behavior of everyone else. My feelings guide how I behave and they guide who I choose to associate with. Outside of that, it's not my place or my business.