MY view of employer/employee is like this: you hired me to do X in the manner of Y which is how you have had the work done previously. Now I perceive that job X can be done in the manner of Z at great savings and increased profits. But you expect me to give you that new process for nothing addtional despite having paid me no more than necessary to have the work done in the old process.
No way.
I refuse to sign the intellectual property agreements unless fairly compensated. And have been hired anyway.
If she claimed that by contract it was shared or hers, fine. But if not, it is not hers, it is theft by her to take or keep it.
Further, however politically inconvenient it is, it is up to the employer to decide what to do with it. In this case, they may have shared it with others, they also now give some or all of it to her.