How could it be that EVERYONE from the home care agency is so bad according to Mom?

The more mom has decline physically and mentally the more I've had to rely on a home care agency. We use one that is very well known and you see their commericals A LOT on TV and ads on the radio -- I don't want to name names. A pattern with mom has developed and it goes like this. S he loves them at first and then they either become mean and say hateful things to her or they scream at her. The first complaint from mom was for a screamer so I reported this person and actually had the bill knocked down because I did not believe I should pay for abuse. I believed every word my mom said about it. Now, I have my doubts. I sometimes get accused of screaming when I'm not. The latest one she loved just a few weeks ago and then this past Thursday she never wanted to see her again b/c the woman asked her why she changed the TV channel all the time. I'm not saying these people are perfect -- I've had to tell some of them pretty basic stuff (Hard for me to believe they have all had CNA training but they have) like don't run to the opposite end of the house when my mom is on the toilet because you can't hear her -- yet they act like there is some vortex in the house that sucks them there as soon as they put mom on the throne. So I know some of these ppl aren't the sharpest tools in the shed but I'm finding it hard to believe that they are all out to get mom. I told mom I want to set up a nanny cam to record this. Mom informed me that the agency is telling them to treat her like this. I know I'm dealing with dementia here but I'm in a bind. I'm not here when all these 'terrible' t hings transpire and since I know mom's losing it I cant' talk her into making sense. I've just been going along with her and saying I'm sorry and yes isnt' it terrible meanwhile doubting the validity of much of this. As of now I'm back to NO respite care and I only had it 2X a wk for 4 hr shifts. I'm at my wit's end. I'm going to contact mom's neurologist @ a dementia test @ the Thanksgiving holiday. I could use some advice b/c this can't go on like this.