Niece and grandmother
When my niece was 3 or 4 years old, my grandma was really sick and on hospice. My niece had never met her, but while we were on our way to see my grandma, my niece told her dad that grandma had died and she was happy now. She says that my grandma came to visit her. I know that the dead don't come to visit after death, but is it possible that my grandma came to see her before she went to heaven?
God, of course, can do anything. While God miraculously relocated Philip after he baptized the Ethiopian eunuch (Acts 8:39-40), we do not look for or demand that God act in similar ways today.
Having been very young once ourselves, you and I both know that it can be challenging at times for a young child to differentiate between reality and imagination. Even adults can want something to happen so much that the event does take place in their minds.
What we can be sure about is that a young Christian child and her Christian grandmother will see each other again (1 Thessalonians 4:13-18). For that, we thank and praise God.