Can I restrict my sister's access to our Mom?

To save my sanity. It has become quite clear that my sister's behaviour is triggering my Mum's dementia. I have been the primary and often the sole caregiver for my 94 year old Mum for the past five years. Mum scores 10 on the MOCA so it is moderate to severe but she has a lot of her personality in tact and does not often go into "true" dementia episodes (1 - 2 per week). I have committed to reducing my Mum's confusion in every possible way. The better I am at this the less difficult it is to care for my Mother - the better it is for us both.
My sister was very badly wounded & abused as a child and I have tried literally 100's of times over the years to help her face and deal with those issues. But we grew up in a fundamentalist religion where medical treatment and especially psychological counseling was very clearly a lack of faith and was - considered a way of introducing the devil into your life. Very likely she has ADHD and also no understanding of boundaries - due to co-dependency issues. At 55 those habits and her adaptive and manipulative behaviours are very deeply ingrained in her world view. She also has no tendency to self-reflection and is generally not willing to take responsibility for her actions - there is always a ready excuse for everything. She has gone from bouts of self blame - constantly accusing herself of character issues and a constant stance of denial relative to any substantive issues. The main challenge is that my Sister comes and goes from my house absolutely as she pleases - I have giving her the choice of any-day and anytime - just that it be a consistant time each week, but for the last year she has only came at the set time and day twice out of perhaps 100 visits - with hundreds of txt messages with every alteration - and then often no warning. I never know if she is leaving in one hour or staying three days - neither does she. Her life is always in chaos and out of control so there is often a reason for her change of plans - or its due to her internet addiction, or her two or three visits to coffee shops per day - or her dollar store addictions. She has lost her job as a PSW so many time there are no more agencies for her to work at - and now she has no work. It is SO sad - she has so few friends and is so dependent on conversations that are often a litany of pain or problems - hers and others in her church. Of course I could go on. But that's a snapshot. The main issues is that I have a lot of anger around her behaviour - it has made a very challenging situation with my Mother much worse. It would be a terrible blow to my Mum if I banned my sister from my house. It might tip her off this fine balance that we maintain. It also could lead to my sister's suicide or very likely self-destruction. I have had NO luck with any requests of altering her behaviour in any way. She feels complete entitlement relative to her right to the house and even directing the caregivers I have hired and instructed into chaotic tasks when I am not here. There are absolutely NO limits as my sister is completely co-dependent on my Mother - like an addiction.
I do have an idea that might work and want some advice or alternative suggestions:
If I give my sister the caregiving schedule marking the times that she can visit - with one possible overnight - then she can come at these set times if she is able - but not at ANY other times. At other times the door will be locked. I know this will lead to BIG conflict and even the police. But if I get her husband - who has had no small challenges with my sister - he may also support this initiative together with my Brother and Sister-In-Law. If we present this at a family meeting it might be better? I am thinking that I need to present some treatment options - but as I've said I've done this literally 100's of time - to NO follow through - so I feel like I've just had it energy wise for finding solutions for my sisters pain. I am looking after the caregiving and trying to keep my work from home going - major challenges there.
I have Power of Care - which my sister was a witness to. There is no money except for social security - as my Dad left my Mum with nothing - so there's no money to argue over - the house is rented not owned and I pay for most of Mum's care (beyond her small monthly stipend) - my brother has just started to contribute a few months ago - up to this point he maintained a complete denial of Mum's condition.
I have recently begun therapy for anger issues.
Any further suggestions would be appreciated.