Women travellers are advised to accompany someone preferably a male companion especially while travelling in rural areas. Although women are generally treated with decency, travelling alone might make you vulnerable to harassment form some drunken male or petty thieves.
Sex is still a taboo in Nepal. Women in Nepal are expected to cover their body fully with clothes. Although the urban areas, and especially Kathmandu, are less restrictive, decency in Nepal requires women to wear unrevealing outfits.