Is she seeing a Psychiatrist? A Neuro/Psych may be able to help. My old Neoro was a Psych and it came in handy for me on occasion.

Sad Sister, praying for you and your sister. I understand wanting to be with ones who have passed. This is not a bad thing to want, is it? As long as she realizes we have to wait until God calls. Praying for her to have peace. I have not had a lot of peace lately either, cry every day. Pray for me too!
I used to have feelings like being drunk decades ago soon after dx. Later these diminished. I would not say that was a primary experience of mine now. I do have some vertigo caused by the smoke irritation of my eyes from the wildfires we have been having in the Southwest. But that's not like the drunk feeling. I am on the Swank diet for decades now, and I believe it may have reduced some of my symptoms, such as feeling drunk, staggering, etc. I can't say it would help her but i can say it helped me.

i think it's time to get some professional help for your sister.
call her dr and tell him what you've told us and what is happening with her
physically and mentally.

i think she needs some professional intervention to help her.
that will also take some load off of you. they will know best what to do.

God Bless you both.