Depends on the parish - because it is a cultural thing.
In all Monasteries: Yes (and only dresses - no skin showing from the neck down & no make up) - in fact, if you arrive, not dressed appropriately, they usually have clothes for you to wear over what you came in wearing.
In the Russian Orthodox Churches: Yes (and only dresses - no skin showing from the neck down & no make up)
In the Serbian Orthodox Churches: No (but women/girls should be in dresses rather than pants, make up is fine)
In the Greek Orthodox Churches: No (pants are just fine - although usually the women wear suits - jackets/blouses with either pants or skirts, but not always - make up is fine)
OCA - anything goes for both sexes for the most part - often times you’ll see devote members wearing burkenstocks (did I spell those shoes right?) or open toed sandles, shorts are not unusual - especially during Vespers the night before Divine Liturgy - but some of the women do wear veils, but it’s unusual.