However, running only 100&200 is some kind of specialization too…
I totally agree with NumberTwo. She should compete in wide variety of events to try her out and to develop her full potencial.
For example our national champion and the only “white” 2007 World Champ Finalist Matic Osovnikar was running 400m till he was 21 years old and came to 10,32 (100m) and then switched to 100m. He now holds a PB of 10,13. Running 100/200/400 in his childhood surely did not affect his speed development.