[bubbacluck]

In this case, no authorization means fraud.

You are correct. If she didn't authorize the use of her signature then it would be fraud.

As others have also stated, there are always clear instructions on what that stamped signature is to be used for.

[exit82]

Correct.

There is a concept called “delegation of authority” in every corporation.

If you are not in the chain of the delegation of authority and for the proper reasons, you are committing fraud.