wellnowwhat

Asking your stepmother about her new career is not "telling" or "gossiping". * She has, after all, posted it publicly.

And a comment to the effect "I must admit I was worried when I saw your marital status changed." is also appropriate*. She did it publicly. Not a secret.

Her reaction to your questions can be read by her husband, hopefully.

I would take a screen shot of her Facebook page first.

I think if my kids knew something and it was something I needed to know, I would feel betrayed if they didn't tell me. Not lecture me or give advice, just give me the information, without embellishment or bias, and leave it with me.