The circle with a dot in it is the Circumpunct, also known as the Solar Symbol. It's not generally depicted with the line at the bottom, which I can see in the film is indeed a straight line with no arrow or cross. There is a circle without a dot with a line drawn off of it to represent a Conjunction of planets. Perhaps the symbol is supposed to indicate a Conjunction with the Sun? You can see examples of the symbols here.
— Solar Symbol
Truthfully, I suspect that the filmmaker made up their own symbol. The director, Michael Paris, has an email listed on his webpage. I sent a message asking if he could elucidate and he responded:
You are right, on the Witch's forhead, this is a circumpunct, a logogram
for the sun in Egyptian hieroglyphs.
The stroke under the circle is just merged with the circumpunct for design
Thank you for your interrest
So I was right that it's a Solar Symbol, but reaching by adding the Conjunction, although he sent a follow-up message:
But your "cunjunction" hypothesis is pretty interesting.
Thanks for bringing that up