My 11yo is about that height, and she wears a 14/XL in Gap and Old Navy. She’s average weight, but broad through the shoulders and chest. But I’d suggest erring on the size of larger, so your recipient can grow into things.
Style-wise, mine likes Kohl’s, Target, and some Gap and sporty Athleta Girl things. Nothing at Gymboree would fit her now, and she outgrew their styles a long time ago. Very ruffle- and bow-heavy.
She really loves the super-stretchy “ballerina“ skinny jeans from Old Navy, which have elastic tabs inside the waist to make them adjustable. They’re pretty forgiving, size-wise, because they’re so stretchy.