User blog comment:Jopjopjop/Volume 19 Spoilers/@comment-186.144.153.69-20150412194423/@comment-16281343-20150412195412

Tosca: A girl that looks like a 12-13 year old girl with white hair. She was with Kiba in the institute. She survived as she unconsciously used her barrier-type SG and sealed herself off. The barrier stopped her aging that's why she looks like the way she used to be.

No one from the Church knew how to destroy the barrier up until the Alliance between the factions. If not for the technology of the Fallen Angels, she would still be sealed.