I'm surprised she's still small enough to fit in those....
Girls typically finish maturing physically at 18 (some earlier and some later of course) and at the time of Girls und Panzer, Anzu should have been 17-18. Meaning she had either already finished her growing (or lack of) or is nearing it's end. So it's not all that surprising if she stayed the same size even in her late 20s. I would imagine the same fate lies for Mako, Katyusha and Sodoko. The freshmen still have time.
