Elizabeth and Mary Tudor met on many occasions both as adults and children. For a time they lived together at Hatfield when Elizabeth was a very young children and Mary in her teens. They always had a rocky relationship over matters of legitimacy and religion which at times lead to one or the other leaving the country. But we have numerous examples in which they met later on. We know for example they both met with Edward during the Christmas of 1550 during his brief reign and Elizabeth was by Mary's side when she delt with Jane Grey and there's numerous other examples.

I suspect who ever told you that is confusing Mary Tudor and Mary Queen of Scots.