Many workers actually sort of enjoy mindless repetitive busy work since it makes you brain feel like your achieving something vs difficult work where you might spend weeks stuck on the same problem.
Case in point:
A fair number of years ago I worked a non tech office job for a few months.
Basically a large portion of the job was checking though a spreadsheet looking at figures and checking them against a corresponding row in another part of the sheet. Assuming the figures matched you would copy the figures elsewhere in the sheet, append some characters to them and mark ones that were wrong in red. The data I think came from some legacy database.
There were a few more steps that I don't quite recall but basically they provided a list of instructions on how to do this part of the job and I immediately recognized that this was basically psuedocode, there was nothing "human" required at all.
They expected a human error rate of around 1% with this and sheets were often checked twice.
A few days into the job I decided to try writing a Macro to do this job, so that night at home I wrote my macro and emailed it to myself. Next day I loaded it up, ran it and then checked the results by hand. I did this until I was satisfied that the error rate was 0.
Next few days I just started running my macro instead of working by hand, meaning I got about 3 hours work done in under a second and could spend the rest of the day doing other (marginally less monotonous) work.
Now in this office they tracked people's productivity levels as well as their error rate, so naturally I end up with obscene performance stats and no errors.
So the team manager of course asks me to explain myself and I show her the macro and offer to show her how to set it up on other computers and explain how well I tested it etc. The response I got surprised me somewhat.
"You are cheating your stats!" was what I was told. Of course I explained that it wouldn't be "unfair" if everyone had the software.
Now at the end of every month they had some (cheap) prize for the person with the highest productivity and lowest error rate and since other tasks were not so easily "scored" the spreadsheet task was a big part of the deal.
No matter how I tried to explain it was like hitting a brick wall, because in her eyes I was "cheating". They had been doing this monotonous work for so long and were so used to it that wasting probably hundreds of man months was preferable to questioning if there might be a better way.
Of course I offered to forfeit any "prize" I might win (despite potentially saving them thousands of pounds), but no we type figures and then somebody wins a prize at the end dammit!
I imagine this sort of brain damaged thinking is common in far more organizations than you might imagine.
Your team manager made a career out of incentivising busy-workers, then suddenly one of the workers come along and proves her, her work and her neat floor of busy-workers pointless? Of course she's going to push back. Nobody likes to be made pointless. That doesn't make her any less pointless, and it's for the better of everybody that she stops being pointless.