They are both correct, though the first is more natural. I don't think there is any need to think of an implied 'who is' in the first. Wearing is participle modifying 'girl'.
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hanuman_2000Are both sentences correct?Yes.
hanuman_2000Is 'who is" implied in (1)?Yes. "wearing blue jeans" is a participial phrase, which has been changed into a relative clause in the second sentence.