My mom is having urinary incontinence with a particular caregiver. What's the best way to address this with the caregiver?

Create a toileting schedule with all the caregivers. Mom should be placed on commode every 2-3 hours while she is awake. While at it, create a schedule with mom's caregivers for her daily care: time to wake up, times for meals, time for nap(s), time for activities, times for hygiene... Most people with dementia do better with consistent routines in a consistent environment.

Lakegirl2: Pose this discourse to the fill in caregiver.

Incontinence with a particular caregiver. I am still trying to figure that out. So either this person gives her more to drink, doesn't remind her to use the toilet, or makes her laugh so hard she pees. Or Mom could be allergic to her and have accidents when she sneezes. That last one actually makes sense if this person wears a strong scent.

Ask the "fill in" caregiver to take mom to the bathroom every 2 hours.
Does not matter if she has to go or not, the caregivers should take her. (they should all do this not just the fill in caregiver)
Are you there when the caregiver is talking to mom If so if you hear that she is talking fast and not allowing mom enough time to respond you can say something.
Some of the things I made a point of doing with my Husband is:
Lowering my voice, not the volume but talking a bit deeper if that makes sense.
I think the higher pitched voices are more difficult to hear and understand.
Speak more slowly and enunciate.

I read a while ago that it can take someone with dementia 45 seconds to hear a question, process the question and formulate a response. I don't know about you but most of the time in 45 seconds I am onto a totally different subject. So to slow things down requires some thought.
Your replacement caregiver might not have the experience with people with dementia and if you help clue her in it might help.

Here's what I did.... I got a pale for just her changes and a notebook. Everyone had to document document DOCUMENT. I told both caregivers it was important, (especially with senior women) to keep clean and dry in preventing infection. Didn't have any issues of that. Since I was there, I was able to oversee this. Since you have multiple caregivers, if I understand you correctly, you can address all of them in this suggested protocol under the guise of "infection control". I firmly believe that being proactive is a must.

If your mom’s urinary incontinence was anything like my mom’s, a schedule won’t do much good.

My mother could use the bathroom and be walking out of the bathroom and have to turn around and go right back in to pee again.

She had to switch over to wearing Depends regularly. It’s a tough issue to deal with.

If your mother has moderate to severe dementia, why are you taking her word about the fill-in caregiver not talking enough or watching too much tv?

Look, if you have regular caregivers who work a schedule and occasionally a fill-in has to be sent if one of the regulars is sick or on vacation, just deal with it.

I was an in-home caregiver for 25 years and I'm going to tell you truthfully. It's never in a client's best interest or their family's to get fussy and knit-pick.
If your mother has good aides who are doing right by her, don't carry on about her peeing herself too much when there's a fill-in.
The aides need to be taking her to the toilet regularly. Every two hours or even every hour if needs be.

The cause of her peeing herself all day could also be because there's a disruption in her daily routine because a new face is there. The slightest disruption in a daily routine when you're dealing with someone that has severe dementia can make huge setbacks.

Tell that caregiver to speak slowly with Mom and take her to the toilet every 2 hours.

Give everyone mandatory scheduled times to toilet Mom.

Incontinence is one of the many symptoms of dementia, so you shouldn't be surprised that she's having issues.
It sounds like when this "fill in" caregiver comes that she is not taking her to the bathroom on a regular every 2 hour schedule. Have you verified with them that that in fact she is doing that? And if she's not then it's time to find another fill in caregiver.
And you don't ask someone with dementia if they have to go to the bathroom, you just take them and sit them on the toilet as often as needed.
You can have moms caregivers sign off on a chore chart as to when they take mom to the bathroom if you think that would be helpful, and you can also consider placing some inexpensive security cameras around moms house so you can see first hand exactly what is going on.
If someone has nothing to hide they shouldn't mind the cameras being there.

Your Mom should be taken to the toilet every two hours as long as she is continent. Depends are for accidents. Two hours is common practise. And if Mom still knows when she has to go, she should feel she can tell the aide. And yes, the aide also needs to be told she talks too fast for a mind that cannot process fast enough. She needs to slow down and make sure Mom understands her. You know when they don't, they have that look in their eyes.

Clearly Mom is not getting good care from this caregiver. So it's simple. You sit with the caregiver. You tell her exactly what you just wrote above. She will either step up to the plate or she will not. In either case you will know what to do next.

My mother was hard of hearing. She was able to lip read fairly well when people faced her and spoke slowly. I instructed her caregivers to do this. It worked out well.

Tell her caregivers to face her, talk slowly and don’t speak as they are walking away from her. I hope this will help her situation.

Best wishes to you and your mother.