Devs made a video that confirmed that she went through the Trial of the Grasses (plus in some shots you can see her cat eyes).

I’m assuming that Yennefer helped somehow, given that she was able to keep Uma alive during his Trial.

But also, Ciri knows full magic, not just signs, because Yennefer and Triss taught her, AFAIK. So it seems to make sense that her combat magic is more advanced than standard witcher signs