not to sound rude here but she is dying with cancer. I know if it were me and I was leaving behind my children I would probably be the same way. She wants quality time with you kids. These are her last days. Maybe be more patient with her and give her the love and understanding she needs. I feel terrible for her. Have you thought about how you are going to feel with her gone? I had a mother that was abusive physically and emotionally and she got cancer and died. I thought it would be a relief but even 20 yrs later I miss her. Remember this is not about you. This is about her and time to spend that quality time with her. Of course she is going to be clingy. She loves you.