You could give her as much literature as possible in gender issues along with DVD's, websites, stories of other transsexual people who have trasitioned and succeeded. Moreover, both of you could attend therapy together and participate in a support group if feasable. You could also get her involved with other parents who are dealing or have dealth with these issues. There are websites designed to help transsexual parents and children; maybe looking into these programs can turn out to be beneficial to her?