I went through this with my grand daughter a couple of years ago when my mom died. She was about 3 then.
There are two things going on here.
1. She needs for you to talk to her about it and treat it like a normal part of life. "I don't want to talk about it" is going to make the problem worse.
You may want to seek out some grief counseling for yourself so that you can talk with your daughter whenever she wants you to. She is actually handling it in a healthy way by wanting to talk.
2. She is afraid that you or someone close to her will die also. Again, you may want to counsel with a pastor or grief counselor to decide what to tell her about life and death, but to ignore the questions will only make her more fearful. She figures it must be a very bad thing if mommy is afraid to talk about it.
I understand you can not go to the grave every day, nor should you even try to indulge this any more than if you would go to a toy store every time your daughter asked.
A simple, "Not today sweetheart, we have other plans" will satisfy her most of the time.
But do take her often for awhile. I took my granddaughter many times in that first year, and she too sat on the grave and talked to great grandma, and then she prayed, then got up laughing and ran and played among the flowers and the other graves. It was very sweet. Like something in a Hallmark movie or something. I actually found myself enjoying these visits.
Because we didn't obsess over it, but didn't discourage her either, in time she "got over it". She looks at pictures of her occasionally now and tells people "That's my Sweet Gramma". (She always called her that ... she calls my dad her "Cute Grampa". Don't ask me where she got those pet names ... she came up with them all on her own. LOL.)
Only on special days like Christmas and Mom's birthday, does she ever ask to go to the grave now. Even then, she says a quick prayer, talks to Gramma, leaves her flowers, then blows her a kiss goodbye and we leave.
We also explained to her that Gramma is not where we left her body, but she is in Heaven with Jesus. When she asks if she can go visit her there, we tell her yes, but not until it is her own time to go live there, too. In the meantime she can "leave messages" for her with God, or visit her body at the grave. She likes that.
Just try to be patient. I know it's hard when your own feelings are still so raw, but you will find that by helping your daughter you are also helping yourself to heal.
Different people need to grieve and work things out in different ways.
I think my hardest day after my mom passed was one day when my grand daughter was looking at one of my mom's many nick-nacks around the house. She was asking questions about it, and I was answering them. I told her that all these pretty things around us were reminders of Gramma and part of her (Gramma's)heart because she had picked out each and everyone because she found it to be beautiful and wanted to decorate her house with it, so in a way, part of Gramma's heart is still with us in these pretty thing when we enjoy looking at them. That is what she intended when she picked them out and placed them around the house. It was at that point that the whole loss hit me like a tons of bricks and I couldn't help my tears.
But you know what ? That was ok. It was good for my grand daughter to know that it is ok to cry, ok to miss someone, ok to talk about them and remember them, and it is ok to know that life will go on.
God bless you both,
B.