What did women wear during the Rashidun caliphate?
Each major grouping and sect of Islam relies on its own Hadith compilation for legal guidance, and over time and in response to regional requirements historic judgements were clarified or superseded. So there is no universal ruling regarding the nature and character of "proper" dress, including female veiling. Fashion History
However, meanings are imprecise and, until recently, many scholars assumed that repetition of a specific garment term over centuries and across regions signified that its meaning and appearance remained unchanged and universal; this assumption has not fostered academic interest in the subject.
One addendum to Mark's answer, from the same source,concerning the time just after the Rashidun era, in the section on Umayyad and Abbasid Dress:
Chroniclers wrote extensively about such conquests, but little on dress matters...
With the establishment of the Islamic state, there was no immediate change in dress if only because non-Muslims, then the majority of the population, were required not to dress like Arab Muslims
So the majority of the population dressed in whatever regional dress they wore before.