Artists often paint or draw subliminally. She was, in my opinion, a closet lesbian. It is SO obvious.
The reason I say this is because my ex wife was also a closet lesbian. She, like O' Keefe, was an artist. She LOVED O' Keefe's work. She also LOVED to draw naked girls all day long, sitting and staring at them. She would rather look at naked girls than anything else. She also did lots of vagina-like drawings and paintings. She always tried to befriend very feminine, petite and beautiful girls and dominate them. She was a very big and masculine person, not feminine at all and NOT good looking.
From what I know about O'Keefe, I would say that she was a lesbian, therefore the intensely sexual imagery.
For O' Keefe and my ex, it was a safe and socially acceptable way for them to express overtly sexual and homosexual images while explaining them away as "just art".
She may not have intended them to be sexual, but she was very sexual anyway. Her subconscious desires came through in her work.
That is my opinion.
Was married to a closet lesbian 21 years.