From what I've read, usually the MOB sets the "standard" for dress. She buys hers first, followed by the MOG. If everyone gets along and the SMOB will be sitting up from with the bride's parents, the SMOB picks her dress after the MOG. If not, she's considered a guest and dresses accordingly.
But, in this case, the MOB is probably not even attending (she doesn't speak to any of us right now), and the bride considers the SMOB (me) as "more of a mom for the past few years" (bride's words). So, does the SMOB lead or follow in this case?
My step-daughter is getting married in July 2020, so I have lots of time to figure this out. But I don't want to create unnecessary problems along the way. Please share your thoughts and experiences!