Susan, it is my understanding that intercourse breaks up and further spreads
the cultures.  She says that she has vulvar yeast, not vaginal.  Often, it's
the vulva that show the first symptoms; she probably has it in the vaginal
canal as well, but is asymptomatic in that area.
     She can treat it locally, of course, with creams or yogurt, but if the
problem is recurrent, she probably has an excess of yeast in her system.  In
this case, she could go with an oral prescription and or dietary methods.
 For more information, any of Dr. Crook's (William?) books are
excellent---they are "The Yeast Connection" and "Women and Yeast (?) or
something like that.  Sorry I can't remember the exact titles---my copies
have all been loaned out!

Constancia in chilly, snowy Michigan