It's not unusal for people to try drinking before they are of age. In fact, it was
de rigueur in California colleges in the 1950s & 60s! Very often the first experiences are not pleasant. So, I'm sticking to my theory (hypothesis?) that we have a picture of Ann, an innocent 17 year old, drunk out of her skull, being goaded by an older man to bare it all and be photographed in degrading poses. After a few sessions of "art" poses, she finds herself preggers. Does she tell her father what his good buddy did to her? Or, does she latch on to the only other black man who is convenient? She may never have even told Obama that she was pregnant when they started "dating" because it looks like they didn't date that much. But she traps him into a sham marriage to keep from exposing her father's "hero", FMD.
Bizarre? Yes. But not unheard of.