I recently came across an article from Psychology Today...
https://www.psychologytoday.com/us/blog/resolution-not-conflict/201909/parental-alienation-what-therapists-need-knowWithin the article is a link that I thought was helpful because it gives suggestions for responses, it's near the bottom of the article... "Amy Baker and Paul Fine (2008) delineate
17 strategies of alienating parents, then offers suggestions for targeted parents about how to respond to these tactics."
It might be helpful at the very least with the kids you still have at home, because yes alienation can happen within a marriage. You might consider a Therapist for yourself to assist/support you with strategies to help minimize the alienation that continues to go on in the home and help with ways to reach out to your 18 year old.
Here is a link to more on Parental Alienation from this site...
https://bpdfamily.com/message_board/index.php?topic=104479.0Your 18 year old is more tricky because she is an adult living on her own, and if she chooses to be no contact that is her decision. Because of her age and because you aren't divorced you can't force contact through the court.
In terms of what to say to your daughter if it were me... I love you, I miss you, and would love to reconnect.
Panda39