August of 1961 would have been in the middle of Summer Break. It would not have been inconceivable that she would have gone to Kenya for the Summer to visit his family.
Stanley Ann Dunham dropped out of UofH after the first semester Fall 1960 (per a freeper post in one of these BC threads).
Supposed “marriage” of Obama Sr. and Ann in February 1961 in Hawaii (various sources, try theobamafile.com for photo).
Where was she from February 1961 until August 1961?
Next known appearance is Mercer Is., WA in late August 1961 with her new baby (per the friends she visited there, no link, sorry).