Hello Cindy,
Welcome to this safe place. Folks here understand, as we have been through similar trials. This stuff is certainly not easy. A good place to start is to read (and re-read) the Detachment Article at the top of this forum.
(Here is the link to it >
Article on Detachment )
It sounds like you understand the situation and your need to detach.
In spite of this I miss her or the way I wanted her to be.
This is one of the hardest things to come to grips with. Our children are now adults, and many have grown into different types of personalities that we would not normally choose for friends and acquaintances of our own. We need to let go / to lose our dreams and expectations of what we wanted them to be and had hopes they would become. Those were our dreams / not theirs. They must find their own way. For me, I think fretting about losing expectations comes from a determination to want our own way.
I was/am a good mom, just don't understand
You are right. We do not understand. Can we ever understand another person fully? They have their own thoughts, bodies, and souls, and make their own way as they understand themselves. The loving detachment is needed to set both them and ourselves free to make our own lives.
Surely, we may miss these adult children / may find it hard to let go, but it is necessary loss. They are no longer the small charges we were given for a season. While we will always love them and want the best for them, our purpose now is to set boundaries to care for ourselves and learn our own strength and peace. Only this will in turn help them.
Take care. Stay with us here. Their is a wealth of wisdom, support and strength on this site. We are all in this together. This is hard stuff, but know that you are going to be alright.