References to Hitler/The Holocaust

I've noticed these things too, and I wouldn't be surprised if Dahl intended these parallels between the witches in his story and the Nazis. He was in the Royal Air Force during WW2 and in one of his autobiographies he wrote about serving the Allied forces in Greece when the Germans were invading, so it's likely that he might have had some prejudice towards them. I don't think that it's meant to be a serious metaphor, I think he just liked to poke fun at Germans in his darkly humorous way (e.g.- the Grand High Witch's accent). If you read Charlie and the Chocolate Factory, the same kind of thing comes up with the characters Augustus Gloop and his mother. The original Willy Wonka movie has lots of German stereotypes in it too! I don't think you're crazy for noticing those things. It's sort of similar to how Mel Brooks loves to play around with German stereotypes in his films.

The movie might have emphasized these things more because in the book Dahl never gave her the name Eva Ernst or any name for that matter, and it never said she arrived at the hotel in a Mercedes-Benz.

She had the German accent though. She would pronounce W's as V's - Vitches, Vant, Vhere.

it's an interesting theory, especially as dahl is quoted to have said that jews must have done something to deserve the holocaust. he didn't seem to be sympathetic on that level

Very interesting suggestion, although not true. According to the book, the grand high witch's country of origin is Norway and she spoke with a horrible accent in the book. The film makers however wanted a more recognisable accent for the screen, so Anjelica had to speak with a German accent.

Roald Dahl himself had anti-semitic views, that's why some people of the Jewish community expressed views that maybe Spielberg shouldn't do BFG.

Dont forget that the witches turned the children into rodents. The Nazis likened the Jews to rats.