Ciri can’t be a proper Witcher. She can’t do Signs because she is a Source, as Triss discovered. That was at least half the reason her Witcher training was cut short and Triss took over her training before they sent her to Yennifer. The other half being the herbs and mushrooms they were giving her were interfering with her development. She never got the Witcher mutagens at all. Ciri’s abilities are completely different from those of a Witcher due to her Elder blood.