While upsetting they weren’t “forced” - employees are at “will”, meaning if I were to walk off the job I would not be contractually bound to continue working BUT at the same time the employer is under no obligation to provide pay and/or benefits.
I know the above is difficult to swallow, the whole idea of training your replacement is immoral but given the choice of collecting pay / most take it and do it because we aren’t Daddy Warbucks. Essentially the employer has you over a barrel and they are taking advantage of it. The employees should be looking for new work ALL the time as most employers have zero loyalty to its employees.
The MO at BNY Mellon is to do more while paying the absolute minimum on a global basis.
Good Luck to your niece. Network as much as possible, keep the faith.