We use 'how' in exclamatory sentences, generally in this structure:
How + adjective/adverb (subject + verb), as in :
How gorgeous she is!
What about this sentence?
How you've grown!
How I wish I had one of those cars!
Is it grammatically correct?
And if yes, isn't it more grammatical to say:
How much you've grown!
How much I wish I had one of those cars!