What's a Mother to do?

My 27 yo daughter and I have never been on the same page.  She has been so disrespectful to me for years.  I feel when she was a child, my husband now ex-husband has spoiled her by giving her everything she wanted while I never wanted to.  I was diag. with muliple myeloma July, 2013. While in the hosp. for 2 wks she used my car and had people over at my condo. Keep in mind she doesn't live with me and only had my keys to get the mail.  I'm always the one trying to make contact with her. I continue to invite her for dinner, go shopping whatever just to have communication.  Sadly to say she got pregnant in high school and had to put the baby up for adoption.  I stood by her and never made her feel like a sl-t.  She was dealing with so much I would never want her to feel worse.  I have a good relationship with my 31 yo daughter.  The problem for me is the 31 yo can see how she treats me and never says anything.  Sometimes I feel she must agree with the 27 yo if she doesn't speak up.  I've been hurt for so many years.  I've written letters asking her to tell me what I've done wrong throughtout the years but never get a response.  I've gone to counseling and offered to pay if she'd go  but it never happened.  She knows if she needs me I will always be there for her. Do I continue to keep trying for a relationship or cut the ties?  I don't believe my ex-husband bad mouths me but she states he is her best friend.