Is she your only DD? Or your youngest?
These feelings are normal of course because her leaving has left a hole. Literally, there is an empty space in your home where she used to be. And now the time you spent with her is empty.
She's moving on and you are left behind. We all know that cavernous feeling of emptiness after bereavement - whether it be the loss of a person or a pet and what you are feeling now is that isn't it?
That awful feeling of loss.
So, I think it is ok to sit a while with old photos and memories, sob your heart out but do put a time limit on your grief and start filling that hole!
Because your DD is not gone. She's changing and growing. Like the Abba song - slipping through your fingers.
Get yourself a new hobby, a pet, meet pals, go out on some date nights, book a holiday to look forward to.
Anything at all - i would suggest trying something completely new which will take you into a new social circle and really busy your mind.
Keep in touch with DD of course - but let her lead the contact and be happy to hear about her new pals and life.
This is not the loss of your DD, just the loss of a part of Motherhood and that little girl she once was where you were everything to her.
She will be back. And you will be proud of the adult she has become. Let her go, with pride.
And get to work filling that hole!