S.H.
She does not seem to like any form... of communication.
What a hard one.
Why don't you just tell her that you are always there for her and she can contact you anytime.
Tell her you love her, and want her to be happy.
She is an adult... and as an adult who is also someone's child... THEY also have the "responsibility" to keep in touch with their parents.
It is a 2 way street.
But bear in mind, that she is moving out and in with boyfriend.
So as with any relationship, they will have their own lives and a "honeymoon" stage. Meaning, she may not even be around you or contact you for awhile. Its like when a person has a new relationship... in the beginning all the couple does is act like no one else exists. So that may happen, once she moves out.
Hopefully, you are also on good terms with the boyfriend and know him, well? Then if you are, you ALL will have, hopefully, a good rapport even if they are living somewhere else.
And once in awhile, invite them over... for dinner. It doesn't have to be SUNDAY dinner. It can be whenever, or for lunch or breakfast or dinner. Casually.
One thing that will push away an adult "child" is when the parents are pushy or critical of their lives.
And just be a good observer... of her even if she has moved out, so that you will know if she is happy or not, or if her boyfriend is treating her well or not.
And can't you just tell her, that you would like to still "see" her once a week???? For lunch or just a casual thing? Or if not once a week, see what frequency she WILL... be amendable with.
And sometimes, in the effort to attain independence, an adult "child" will seemingly push away their parents. So keep that in mind too.
Just let her know you are always there for her.