Yep, you are all right. My husband was adamant he didn't need a babysitter and I just ignored him and said I was hiring a housecleaner because I couldn't do it all anymore. Of course she does a little house cleaning while here but he has really got used to her buzzing around the house.
When she would sit down and watch a little TV he used to tell her that if she was done cleaning she could leave. haha! She told him that she was taking a break and would finish in a minute and asked him if it was ok if she took a break.
I'm trying to break in another helper but she is a little shy and it will take a bit to get her accustomed to the house and him accustomed to her.
Just try to think of an excuse as to why you need her there.

Tell her it’s a friend of family and they want to come to visit and watch a movie. I do it for my husband.

I write on a white board name of caregiver Our friend and I tell him I’m going to Joanns.

Mine does that a lot. He doesn't "need" anyone but me. I do the angry/guilty thing all the time. Depending on his age, I use a Protein drink to subsidize his eating. He has gotten to where he does not eat at all - then wants nothing but junk food. The protein puts and keeps him on track and he doesn't seem to be so hungry for the other after. He likes the vanilla and chocolate.

Maybe have a communication book with a little information about your Mom's back ground.Where she grew up.What she did for a living.Leave a photo album they can look at

I tried 3 different agencies. A different person showed up every time, adding to Mom’s confusion. I posted a request in my church bulletin and selected 2 people I thought would be compatible. It’s working. Consistent schedules; photos of the caregivers as reminders; the same activities each day. Tell your mother that she is helping you by cooperating. Tell her that you need her to agree to the caregiver, not because she needs care but because you need help. I know I do.