Betty's mother had three children, two of which were boys. She also had a great admiration of coins. Because of this, she named her first son Diamond, for the Dime. She then went on to name her second son Nick, after the nickle of course. What do you suppose she named her third child, the only girl of the three?
Did you read the whole riddle?
Perhaps you should start over at the beginning!
Why, we're talking about Betty's mom of course, so it must be Betty!