As far as I understand, the special dresses for wealthier women (by the way, how come there are never dirty, ragged poor folk at mediaeval re-enactments?) were designed to show that they had servants to put them on as well as being able to afford quality material and accomplished seamstresses. Everyday wear would have been more practical. Even in a castle, you would want to slob around some days.
I found Bernard Knight's Crowner John books to be quite good for basic info on late 12th Century life, including clothing standards. Although styles changed, sometimes rapidly, the basic structures of the clothes didn't, so the descriptions probably hold for later dates.
The dresses, and many of the men's clothes too, were sectional - the arms would be attached with laces, which could be adjusted for fit and undone to wash the garment. As well as lacing up the backs of gowns, there was also the option of lacing at the front of the bodice. Whilst this is now pretty standard uniform in historical and fantasy movies for barmaids, it would make smart dresses easier to put on without help. There were also some that had lacing at the sides - a bit more tricky, perhaps.