I’m fairly certain the answer is no, not a consistent one. I do hear from straight readers from time to time, who were given a book of mine by a sister, mom or daughter.
The most mail I’ve received from readers who identified themselves as straight was regarding Finders Keepers. It wasn’t exactly a tidal wave of mail, but the issues of body image, self-esteem and mothers/daughters are universal.
The women who wrote said those themes in the book spoke to them – and they liked the story, too! Romance is romance, after all, and in a lesbian romance you get double the love from the female point of view. And that works for me.