Sunan Ibn Majah Book 1, Hadith 115
"Men and women used to perform ablution from a single vessel during the time of the Messenger of Allah."
She and the Messenger of Allah used to take a bath from a single vessel.
"Often my hand would touch the hand of the Messenger of Allah while performing ablution from a single vessel." (Hasan)
Abu `Abdullah bin Majah said: "I heard Muhammad say: 'Umm Subyah was Khawlah bint Qais. I mentioned that to Abu Zur`ah and he said: "It is true."