My daughter, who moved here almost 6 months ago to be closer to me and her sister, is mad at me for hanging up on her when she was raging at me, has decided to punish me by not letting me see my granddaughter. Since they have been here, I have had the little one more than mom has, I have provided all of the transportation and provide all of little one's needs when she is with me. She has a room here, an age-appropriate play area in the living room, books, toys, clothes and furniture. Her mom got mad at me when I asked her when she'd be home to have little one, as prearranged with mom, while I went to a basketball game. Mom was prediagnosed with borderline personality disorder as a 16 year old, and the only way to make sense of this is to defer to the characteristics of that disease. Obviously this is hurtful to me, but I am genuinely concerned for little one, with whom I have a great relationship. She is just two years old. I don't want to do anything drastic; best case scenario is for mom to get help, but how when she doesn't think she has a problem. But now she is putting her perceived justification ahead of little one's needs. Any suggestions?

Well you posted this under the Family Law forum. So you can check local laws on grandparent's rights (ANY question on law needs to include your general locale as laws vary by area.), Grandparent's rights have become more common in recent years.

But frankly that would drive a further wedge between you. I would try to enlist the sister's aid as mediator. I would also try to get counseling for yourself to understand her disorder and ways to deal with it.

'Mom was prediagnosed (?) with borderline personality disorder as a 16 year old, and the only way to make sense of this is to defer to the characteristics of that disease.'
No, there is no need to defer to such a diagnosis. You should act the way you would with anyone.
'best case scenario is for mom to get help.. '
Not even to be thought. She is an adult and free to see a therapist or continue to punish you, as she pleases.
These are two extremely important factors to give careful thought to in your relationship with your daughter. No matter how much you have turned your home into a nest for her child, and no matter how good for her you are, you can't allow yourself to view that as a reason why you have certain rights. If you get caught up in the pawn game, the grandchild will suffer even more. Sometimes you have to sacrifice your hurt and just wait for a child to stop punishing you, rather than muscling your way back in.

'Mom was prediagnosed (?) with borderline personality disorder as a 16 year old, and the only way to make sense of this is to defer to the characteristics of that disease.'
No, there is no need to defer to such a diagnosis. You should act the way you would with anyone.
'best case scenario is for mom to get help..'
Not even to be thought. She is an adult and free to see a therapist or continue to punish you, as she pleases.
These are two extremely important factors to give careful thought to in your relationship with your daughter. No matter how much you have turned your home into a nest for her child, and no matter how good for her you are, you can't allow yourself to view that as a reason why you have certain rights. If you get caught up in the pawn game, the grandchild will suffer even more. Sometimes you have to sacrifice your hurt and just wait for a child to stop punishing you, rather than muscling your way back in.
Excellent response.