What can you do when your parents that fall back into old ways?

Im the caregiver for my Mom. My husband and youngest son, 21 live here in her home with her, it has been 4 months since we moved from our old place of 14 yrs and came to be back where I grew up in my old house. I had to come since the doctor would not start the Aricept until I moved in with her, something he did not tell me before so out I came. My Mom is a widower and has a happy attitude about life, always has. When my Dad was alive, they used to smoke like chimneys in the house and drink beer every night, alot of it . Since my Dads death almost 5 yrs now, she hasn't drank and her smoking was stopped. over the course of time, she used to be able to come out to our house for a visit no problem, didnt get lost etc was and was very social. In the last almost 3 yrs, things have changed. My Grandmother was living out here with my Mom since she was alone as well , then had a major problem with her heart and went into the hospital. My Grammas 94. When she got out the first time I noticed my Mom was short with her and very worried about taking care of my Grams new needs. Diet needs, cooking with no salt , giving more meds etc. Then one day at work My Mom calls said Grandmas in the hosp. again. I come out. My Grandma starts calling me daily saying Mom can't handle it please come take care of me. I tell her, don't worry she can handle it. Well, she couldn't and I quit my job to come help out, leaving my guys behind. 3 Months. 3 months my grandma was good to go, her heart was good, they were eating good she'd gained weight, but now, my Mom was smoking alot (stress I figured) but even with the large house They were now stressing out about me being here . OK, so finally after alot of BS, I said if you ladies don't need me I will go back home. So I did! I felt kicked to the curb, but got over it.
Days later My Grandma starts calling (I got my prior job back) with complaints. (not to sound disrepectful, but my Grandma tends to be a drama person, which after 94 yrs ok , go for it but geez ) So for a yr of running back and forth (hour and a half drive each way) So she went to my Aunts for a visit in Colo. a few days later My Mom and I were talking on the phone and she sounded odd. Really out of it. I asked if she was alright it was my lunch break, she said she was and I said ok. After work I told my husband Im going to go over to see if shes ok. She said she'd been attacked . I immediately took her to the hospital and brought the clothes she had been in ( not torn, just kind of dirty) and they did all the things they do there, she talked to alot of ppl the police they came to the house took pictures the whole thing, and no real signs of anything except a broken bush on the side of the house. She acted like she wanted to forget about it and then didnt want to talk to the police anymore, which was odd, but maybe not. never having had a bad experience like that I didnt know.
Then I found the beer bottles. I asked her about them and she denied them. I wondered if she hadn't have just drank to much and made the story up , and felt guilty for thinking that. I didn't put her on the carpet about my thought on that and left it alone. The investigation died as they had zero clues and she wouldn't help them . Mos later her short term memory was getting noticable, repeating things , focusing on her dog (every story ends talking about the dog) and the smoking was more , and I suspected the drinking as well. the geriatric doctor called me and said to have her come in for tests. The found a calcified bump inside her brain. Also, from the tests he suspected dementia. So we went on the 23rd and she told us, yes she has alzeimers. She also told my Mom to stop smoking (my Mom blew her off) and no drinking. with the Aricept it wouldn't be good . After living her now, and her being on the med for the last 4 months, I dont see it helping , or slowing things down. She has even started smoking in the house again after all these years , I asked her please not to, and if you have to do it on the porch (it is so bad for her! but Id rather her smoke then drink ) Anyway,
does anyone have any ideas how to help their parent stop smoking and or drinking in a kind way? I am not her keeper I am here to help and make sure she is happy and healthy .
Thanks for any ideas, try not to judge we are all doing the best we can. Watching her is so sad I can see the disease stealing her memory, stealing her feeling of control , stealing everything slowly from her and we hate it. Luckily, she for the most part trys to keep her good attitude and is usually happy, takes her meds and eats well, but I know shes not to happy having her privacy invaded by the doctors even us sometimes, but family takes care of family , and she has said she's blessed to have us, that makes it worth while when she feels like that and says so.
Thanks for listening to my rambling.