You will know the right time to give it to her because you will sense it. Having gone through the death of a grandchild, I know that having something special will be very emotional but at the same time, will mean more to her than you will ever know. From my own experience, I don't believe she is ready for anything right now, but she definitely will be in the future. Now is the time for grieving but you will know when is the time for memories. It doesn't come easy!