It’s always the least productive coworkers who have the most to say about what other workers are doing, even if the people they’re criticizing get three times as much work done as them.
This older coworker repeatedly criticized how this worker spent her downtime between tasks, while herself spending plenty of time on the phone taking personal calls and having non-work related conversations. This prompted the worker to no longer help the coworker with her tasks, leaving her to manage her fair share of the workload.