Women travelling alone in rural Greece are usually treated with respect. Hassles do occur but they tend to be a nuisance rather than threatening.
Greeks rarely travel alone and so have difficulty understanding why anyone would want to do this, but they have been sufficiently exposed to foreigners to accept such ‘strange’ ways. This applies also to women travelling with a male partner to whom they are not married. In rural areas it is a good idea to dress conservatively, although it is perfectly OK for women to wear shorts, short skirts etc in tourist areas. If you are pestered, ignore the guy, and you’ll find that the hint is usually taken.
The status of women in Greece has been improved by several reforms introduced since 1980, including civil marriage, divorce by consent, legal abortion and the abolition of the dowry system. But remember that changes in attitude are slow in rural areas.