I read some good advice once on dealing with toxic family members, specifically ones you don't see much. for you, set it in stone that you won't drink. get that settled. realize that this lady is going to drain you mentally dry before the visit is done. know that and you will be ready when it starts. it may even help you be more graceful as you endure the visit. go there with your tank on full. by this I mean you will maybe be doing some exercise( walking, whatever) to keep your mood elevated. it also means you can have a book started that really has you interested. that's something you can do while there too, along with walking. anything to have something to do. eat well.
and remember the most important reason you are there, to visit your dad.