I am having a very similar issue. My daughter is 40. We have had on/off issues for decades, but since she had 2 children, I thought she was doing better. I watched those kids 3 to 5 nights a week so she could go to school or work. 9 years. Now, she hates me and has not let me see the kids since before Xmas. Their father has them 3 hours a week and he calls me to come by his house for a visit. I was there last night and she is telling those kids so many lies, like their Dr said they shouldn't see their gramma anymore. I have written her letters, of apology for real or imagined things from 25 years ago... reminding her last 9 years have been great on both sides... more letters, taking full responsibility... she won't take my phone calls, she won't answer my emails and the kids told me if I go over there, she will call 911. I did go to a lawyer and he said bascially, the ball is in her court. I feel she is mentally abusing the kids, they cry for me and she just tells them you are never going to see your gramma gain. I believe she has some bi-polar disorder, that brings on these moods, she lies so much I have no idea if she has ever been diagnoised, she told me 6 years ago, she was dying of lukemia... so this is what I am dealing with. My grandkids miss not only me and PaPa, but all their friends in my neighborhood they play with. They said now, all they do is watch TV. Any ideas?

Oh Goodness! My heart goes out to you. I will tell you what my counselor told me... she told me to quit apologizing to my daughter for the past. That I shouldn't discuss it unless she agrees to do with a counselor. However, I love my grandkids SO much I can imagine myself doing exactly what you are doing... practically begging to see them.
I believe though that it might be better if you do not even discuss your daughter when you see the kids for that short time. Make it all about them. I am sure she tells them things so that they will repeat it and it will hurt you. Then, when they are with you, they see you hurt and upset rather than happy and positive. Just let them know you miss them. If their dad could get them more often, maybe that would give you more time with them. Are you close enough to him to take them all somewhere fun for the weekend... or even a week? I would quit letting her hold you hostage. Maybe if she sees you don't need her to be able to see the kids... and that you aren't trying to get her forgiveness anymore... she will come around. She seems to like the control and the power she has to hurt you. I know this is easier said than done... but, you can only take so much hurt from a person. After a while, you have to just let it go. If she doesn't want you in her life, that is her loss. But, sooner or later she will need you. How long has this gone on this time?

Thank you Star -- We do try not to discuss the daughter. My canned answer is "God would not want me to say anything bad about your Mommy" last night the lies got to me, but I will stick with the canned answer.
Their father, lives with his girlfriend and they do not want the kids more than their normal 3 hours on Sunday, so I am stuck there. My daughter does not know I am seeing them at his house. Again I thank you, I made an appt for myself for therapy, hoping that may help me as well. And you are right, I can see her laughing about all the power she has over me. Its just a shame that she is using her kids like that