Maintaining contact is not the same thing as having a relationship.
I can tell you what worked for me. I skipped the whole dang holiday routine because I could not pretend that things were normal, because they were not.
Picking her up on a street corner and buying her an occasional sandwich worked best. I asked no questions and so she told me no lies. When she hit me up for money, I said no. We talked about the dog, a lot. That's as good as it got back then.