I actually despise the term tween and see it only as a marketing word. However, I've had to use it the past couple of days in order to sort through sewing patterns online for Phaedra. It's been extremely frustrating.
First, she still really likes the patterns that go to a child's size 8, but Oliver and S and Izzy and Ivy and many other really neat patterns stop too small. I'm sure there's a way to do alterations, but this is beyond my skill level. Even McCall,s and Kwiksew have precious little in her size range, and much of that is a style I won't bother with.
Second, she's very far from fitting the proportions of a lady's pattern. This isn't surprising, but I did explore the option when I realized how few girls' patterns go beyond size 8 or 10.
I have spent over two hours trolling through sewing sites, looking for patterns that appeal and will fit. I finally found a few, and the way I found them was the search term "tween". And since I feel credit should be given when deserved, the site that had the most options in her size is Sew Mama Sew.