Harvesting and freezing eggs is typical for FAB who transitions. It's a relatively common practice today.
There are also a number of private Facebook sites specifically developed for parents of transgender children. You can find links to others who are in a similar point in their life.
I would also recommend both you and your child reach out to a therapist with training in LGBTQIA+ counseling. To ensure the therapist is qualified, ask if they are fully credentialed by WPATH - the internationally-recognized professional sanctioning body for transgender care.