LISA - A friend who is a member of the church told me just before I was to go to the temple, that for some time, single women weren't allowed to receive their own endowments. Can this possibly be true? That only missionaries and married sisters could receive their endowments?

JOEL - It is true that for a long time if young single women did not serve missions or get married they did not receive temple endowments(at least not while they were still fairly young).
If you think about it, some of the covenants we make in the temple have to do with our relationship with our spouse to whom we are sealed and the whole reason for the endowment is for those who will be exalted in heaven, which of course can not happen unless we are sealed to an eternal companion.
This really hasn't been that much of a problem because most active LDS women would have gotten married and sealed to someone during their lifetime, even if it was at an older age.
In the past older single women who never married but were otherwise worthy, were allowed to receive their endowments. If not it was done for them by proxy after they died. The main difference now is that single women(and men) may receive their endowments at a younger age.
According to Church policy, worthy single members who have not received their endowment in connection with a mission or marriage may become eligible for a recommend interview when the bishop and the stake president determine that they are sufficiently mature to understand and keep the sacred covenants made in a temple. Such eligibility is determined individually for each person rather than using routine criteria such as reaching a certain age or leaving home for college or employment.