Should we continue to send Birthday cards?

We are estranged from our DD. Our first GS was born in 2015, we met him and have not been allowed to see him since. Our DD had what we thought was a very good upbringing. She graduated from UNI and became a teacher. She left with no debt as DH and I funded her education. On Mother's Day 2015 I received a card telling me I was the best mother in the whole world and how she would die without me. I felt the same and life was good. By the end of 2015, I was the mother from hell.
Basically we shut the bank of mum and dad and would not pay for a kitchen they wanted. They live in a 4 bed detached with conservatory. Both have good incomes and two new cars. Our sil has objected strongly to the closure of the bank and it's caused so much trouble.
We have not had a Mother's Day/ Father's Day card, birthday card or Christmas card since. My DH was 60 last month. I have sent cards for my DD and our DGS (who does not know us) in the past, telling her the door is always open. I have text her to see if they are ok and told her the door is always open. We feel so hurt that that she can and would ignore the fact that her dad was 60 that I feel I can not send any more cards. It's not a tit for tat reaction. We just feel the need to stop torturing ourselves as she is never coming back. Just wondered what you would do?