According to a previous post "Of course, it is basically a sin to not marry and have kids though."
Since that writeup is listed in a node titled "Things Mormons ARE allowed to do," some clairification may be in order.
Specifically, Sheri Dew has been single her entire life and currently serves as editor in chief of Deseret Book.
As mentioned in the above referenced wikipedia article Sheri Dew was a councilor to the General Relief Society President from 1997 to 2002. I can think of no higher position of trust in the L.D.S Church that can be held by a woman than General Relief Society President. Being one of two councilors to this person makes Sheri Dew about as far away from a sinner in the obvious view of the leaders of the LDS church as one can be placed.
That being said, it comes as no surprise that someone old and unmarried might feel out of place in Mormondom. That is one of many ways to feel out of place in LDS culture, but I do not think of a church as a culture. Each church is a community. The question then becomes one of the purpose and belief construct of that particular community. In other words, what do all members of the community have in common. My advice to members of any community is that they should refuse to be offended by other members of the community as long as they share the same purpose, and are able to debate their own belief construct within that community. That has worked for me. Outsiders of any community occasionally want to be offended, so I have other suggestions for outsiders regarding the disposition of single women in the L.D.S. church. I would suggest they consult with Sheri Dew on this issue. She would possess empirical evidence, a commodity we both lack regarding how it feels to be a mature single Mormon without children.