Could just be a ploy to keep the mother out of the courtroom so she won't garner sympathy. If she's a witness, she cannot sit in the courtroom until after she's testified.
Maybe not. Every State has different laws, but in general, there is a thing called a Missing Witness charge and it goes something like this:
If a witness on the witness list of a particular side is not called to testify, the jury would be permitted to infer that the testimony of the missing witness would not have been favorable to the side that listed the missing witness on their list.
If Cindy is on the prosecution's witness list, I would expect her to be called to testify.