What an uncomfortable thread.
I'd be more interested in the answers to whether anyone would let (or feel it was appropriate) for other adults to screenshot and repost cropped images of your 11 year old DD's body to discuss on the internet in a public forum, with a view to shaming an outfit. The question of what one daughters wear could have been discussed without the use of that image.
I don't think what she wears is anyone's business, but would struggle to understand what it is that's on show in that particular dress that suggests a lack of modesty. We are talking about a child out holding hands with their mother, why there needs to be a judgement or implied sexualisation of this at all I've no idea but I'm not sure this is what adults should be doing with their time.