‘ And on his restoring the silver to his mother, his mother took two hundred pieces of silver and gave them to the smith, who made of it a graven image and a molten image. And it was in the house of Micah.'
At the mother's request two hundred pieces of silver were turned into a graven image and a molten image. These were then placed in Micah's house. It should be noted that she dedicated the silver to Yahweh for the purpose of making these two images. That did not necessarily involve the use of all of it, only what was required. Some further of it may however have been used to make the ephod and teraphim. (Such setting aside of things to Yahweh as ‘Corban', with the use of part of it retained until death, certainly occurred later - Mark 7:11. It does not necessarily mean that she was cheating God of the remainder of the 1100 pieces).