My wife (27F) and I (34M) have been together for 7 years, married for 2. Throughout our entire time together, I have seen that she chooses to dress a bit on the modest/demure side. Not covering up too much or anything, but things like wearing leggings and tshirt to the gym instead of tight shorts and bras that most women wear, and wearing mostly jeans, skirts, sundresses in daily life. She still wears bikinis at the beach or pool and cocktail dresses to special occasions, but most of her outfits tend to not show much cleavage or other skin. We live in Australia so not a conservative country, and this isn't the result of some past incident/trauma or anything like that or body image issues, she's in shape and conventionally attractive, just a personal choice of hers since she's shy and doesn't like showing skin publically. She's not conservative ideologically.

Anyway, a few weeks ago was one of her best friend's birthday and it was a big party (100 people) so all our friends were there, along with the hosts' family and relatives. For the first time in a while she was wearing a revealing backless cocktail dress. When dress shopping, she really loved that dress but was a little unsure about getting it since it was quite skimpy for her usual style with a plunging neckline, but I knew she was into it so I asked her to at least try it on, and then genuinely complimented her heaps saying how gorgeous and sexy she looked, which is why she bought it. During the party, when she was dancing, the hook at the back which held up the dress broke open, and the dress fell off. She was wearing underwear but not bra, so she was exposed in front of a lot of people and just froze for a while and then ran to the washroom crying. Now it's been several weeks and she's traumatised about the whole event. I have tried comforting her but no benefit. She refuses to go out of the home now. She doesn't blame me but I also feel guilty because while I didn't force her, I played a big part in her getting it. Looking into therapy but the appointment isn't available for 6 weeks.