My mother's entire personality changes when my siblings visit and she drinks. How can I get her to not drink when they visit?

Ah, this is so common. They are in complete denial over your mother's condition. If you mom is like my parents were, and I expect she is, she gets pumped up over the idea that they are visiting, so she acts "better" than she is. She can only maintain this for a short time. They leave and you are left with an exhausted mom in worse condition that when they came. However, they leave thinking you are overstating her condition. It happens all of the time.
If you use tact in passing this information on to them - not blaming them, but telling them that she tries so hard to be like she was - cooking for them and being mom - that they can't possibly see the effects after she goes. Of course, if they stayed around longer they'd see that she can't keep it up, but suggesting that could cause the drama you wisely want to avoid.
You can let them know that the doctor doesn't think drinking is good for her - that it could even put her at risk for more health problems. You may want to get the doctor in on this. I'm sure you'd get cooperation. You could also ask her doctor to write a note suggesting that your mom take it easier and not cook and try to do so much.
As I said - it's denial on the part of your siblings. They don't want to accept their mom's aging. But they must. So some gentle reminders with medical backing could help. Take care. This is a hard issue to address, but you aren't alone in it.
Carol

You know there has to be a name for this type of pattern - the "she gets pumped up over the idea that they are visiting, so she acts "better" than she is. She can only maintain this for a short time. They leave and you are left with an exhausted mom in worse condition that when they came. However, they leave thinking you are overstating her condition." you so aptly described.

My mom did a game face for years, if we hadn't moved in with her for a period of time after a hurricane where I could see her true day to day inability to manage on her own, she probably would have slogged along for a few more years not getting the care & assistance she needs, living in a constant state of anxiety and worry.
So when I forced her into IL there was no room for arguement on the need.

With my MIL, who was an alcoholic, she would have the visits all planned out to exactly what, when how and therefore could control. The sons really were in denial, it was "mom is totally fine, she had a great time when we did.......". It was only after they started getting collections calls because of her being a total financial terrorist, their having to go & deal with the ER, etc. that their viewpoint changed.

RLP, your family needs a dose of reality. You are just too nice. Can you take a vacation or go away to take a course, go away to visit family, so that other members of the family have to come and take care of mom for two weeks? so they have to see & deal for themselves what mom's like. Personally I'd do it so that they have to take her to at least 1 MD appt & a dental visit. Reality check.

When are parents get older we're faced with our own mortality. Also, when your siblings do come, they are on holiday so they have no responsibilities. Since your family comes in for visits and it might not be practical for you to get away why don't you try to schedule moms medical appointments at the time of their visits. That way everyone will need to get up early (which should cut back on the late hours and drinking) and have them go with with you and mom. Speak with the doctor in advance and let him know the issues and let him bring it up- that should get you out of the middle. Good luck.

One small question -- where does she get the booze? It sort of reads like there is a steady supply right there at home..

Good question. When my father died, the house was left in trust for her lifetime but was actually left to me. Mother is determined to live alone in a house with 3,200 square feet in the middle of a no longer working farm with absolutely no neighbors. I check on her 6 times a day, but she does not want anyone to move in with her yet. She wants to prove she can be independent. The house in almost 200 years old, but in good shape except for her hoarding. Everyone leaves wine and liquor for her when they come (except for me). She uses it until the next round of visits. My husband and I are watching carefully to decide when to step in and take over, but it is a very touchy subject. We really didn't want the house, but it is large enough for Mother to have a nice apartment which she has had an architect design. It takes two weeks for her to return to herself after a visit from one of my siblings. My son, who is 19, helps as he can but is off at college. I feel like Alice in Alice of Wonderland sometimes.Having been a special ed teacher for most of my life helps, but without sibling support I am facing a daunting task. She drives to the only nearby town whose residents are watching after her,too. Mom has always been a tantrum type of person and they became worse after her accident. I am out of school on sick leave due to cardiac issues. A full scale and ugly tantrum is not on my physician's list of desired activities. I feel helpless. My family wants me to look after Mom without making changes. One sibling is in the Middle East, one lives two hours away ,and the other lives 8 hours away and is a highly functioning alcoholic. I am the next to the youngest. The real me would like to make major changes, but my health will prevent that for about two months. I am open to suggestions and criticism. An important factor to know is that my father, who died a year ago, was on just about every board of directors in town including the dept. of family services.The South is notorious for covering up issues.