A very long time ago now, but I had a similar experience. My parents arranged lessons through BSM who would book the test in advance right at the start, because it’s better to have the date then postpone it if not ready than wait to book it when you are ready and have to wait for a slot.
The cut off to postpone was two weeks before the test. As it was coming up I felt like I was still not sure on a lot of the road craft. I asked my instructor if I was really ready or if I should postpone and he said I was fine.
Then, literally 2 days before the test, far too late to postpone it, BSM called to say "we have a duty for the safety of the examiner and the general public and we can't allow you to take the test in our car" ?!!!!
So, given it was too late to postpone it I took it in my parents' car. Failed, obviously, but not especially dangerously, just clearly not ready.
I got another instructor via recommendations, he was excellent and I passed on the third attempt (second was pretty much perfect for all the normal driving but I messed the reverse round a corner alignmenr twice so no way I could pass. Third was basically perfect).
With the second instructor I realised how much I had just not been taught in the first lessons. Not even the "mirror-signal-maneouvre" drill.
Thing is, the first instructor had taught people I know who passed. So I don't think he was a cowboy or anything. Just totally wrong for me, and somehow he'd failed to recognise I wasn't progressing properly until far too late.
So, I passed, and I drove happily and confidently as a new driver and have done ever since, 30+ years, cities, towns, motorways and country roads, UK and abroad, with no issues, no accidents, not even a speeding ticket. It wasn't a sign I was destined to be a terrible driver, just a bad start.
Anyway, a long anecdote and long time ago - my message for OP is just that this does happen, it's not the end of the world, chalk it up to just a clash of styles, it's not a reason to lose confidence in her potential to pass next time, just a signal to try again with another instructor.