maybe she just wanted those creepy eyes

To follow in Geralt’s footsteps imo. She was always adventurous even without the threat of the wild hunt after her. She may also not want to use her elder blood powers to avoid the Wild Hunt/the Aen Elle discovering her again.

Also Ciri undoubtedly has trauma surrounding fertility and pregnancy. In the books she was repeatedly captured by people who only wanted her in order to give birth to another child of the elder blood.

Thinking on it, they could further justify it by having ciri decide to become infertile to avoid others from trying to capture her and force her to conceive a child of the elder blood.