Hi tryingtobeme. I am sorry for the loss and grief you feel. I think it is very telling of how much this person means to you. Expressing that to them in a way that emphasizes how much they mean to you and how much they helped you takes the focus off your own sadness and maybe lifts them up in their grief and sorrow.

It is sad that is not your mom but it is wonderful that you found someone that really helps you. It is tough to let go, but why not at least try to help them realize how much they have given others so they can face death knowing how much meaning their life really had.

For your own grief, maybe a grief support group or counselor may be helpful.

If you cannot tell them verbally how you feel you could do a journal or write a letter until you are satisfied that that is what you want to tell them. Then tell them or read them the letter. This is one way to bring joy to someone facing the darkness of death.