Typically, this process of separation from one’s parents begins during adolescence, but you might not have been prepared for it, because of the nature of the relationship you two had
Your daughter’s revelation happened to come at a time of transition in every parent’s life: your child becoming an adult. While you’re losing whatever the experience of having a child you assumed to be a certain gender meant to you, you’re also losing what every parent eventually does-your role in your child’s life, which changes dramatically when kids leave the nest and head to college or begin to live independently.
You describe being very invested in every aspect of your kid’s childhood-staying home to provide care, giving “input on clothing and hygiene” well into adolescence, even using the phrase “best friend”-and maybe this investment had something to do with your difficulty getting pregnant with your only and long-awaited child. But there’s a difference between being friendly with one’s child and taking on the role of best friend. What kids and parents both need are best friends their own age. When a parent takes on the role of best friend, that parent may feel abandoned by the child who is doing what she should be doing as she launches into adulthood, which places a huge burden on the child and leaves the parent with a tremendous sense of loss. It might be helpful to consider that you would experience this kind of loss in your life as a parent at this point in your child’s development, regardless of whether your child came out as transgender.