OP, unless your 16-year-old has experience of what is appropriate for a law firm's retirement party, I would tend to pay her no attention. 😉It looks fine to me - plus (controversially for this thread) I rather like it.
I suppose if you're really concerned - and given the occasion, I don't see why you would be - you could always have a word with one or two of the other women going to the dinner. I wouldn't bother, though. You like it and it fits and is comfortable, go for it.
I worked for a City solicitors for years, and nobody ever noticed (let alone cared) what people were wearing, unless it was really wildly inappropriate - think jeans in a corporate client meeting or a skin-tight scarlet leather mini-skirt to meet an elderly widow.