She's a beautiful woman but that was an inappropriate dress to wear to a wedding. You are NOT supposed to try to outshine the bride, and that dress shows so much skin (and is so tight it leaves nothing to the imagination) you can't help but stare at her. I understand that she is confident and proud of her body, and with that body I'm sure she can wear almost anything she wants, but as I tell my kids: just because you CAN do something, doesn't mean that you SHOULD. Buy something a bit more modest to celebrate with the bride, and save the skintight dress for going out dancing with your husband.
To answer you question--no, it's not body shaming, it's the shaming of a rude, self-centered person. What she reports happened to her is wrong and shouldn't have happened because publicly shaming people is wrong. But what she did was wrong too. All the parties involved in this incident behaved badly and should share the blame for ruining this poor bride's wedding.