It probably wasn’t. She probably wore a man’s hat; she was notorious for wearing men’s clothing.
The trilby, which is pretty much the same hat with a narrower brim, was around before. The name fedora was from her role, but the hat pretty much existed before.
By the time Jews wore it with the name fedora, it had already become a popular men’s hat.
It’s not a symbol of holiness at all, it’s a hat, for crying out loud.