I read about her some time ago. The only evidence is a book written by someone who knew her with zero evidence to support it.
Tubman could not read or write.
I don’t doubt that you will find thousands of stories about it but no real proof.
What is your problem with black history and its heroes/heroines?
Same with the Culpepper spy ring. Clandestine activities leave very little documentary record. It’s a feature, not a problem.