This is something that I've been curious about too but it is entirely skipped over in history books on the period, I think because it was not something that was really spoken about. We have had discussions over at The Elizabeth Files forum about menstruation - see http://www.elizabethfiles.com/forum/tudor-times/menstruation-and-tudorelizabethan-times/ and we think that women would have used rags (cotton cloth) to 'mop up' the flow.
There is an interesting article on Elizabethan attitudes to menstruation at http://www.thefreelibrary.com/Attitudes+towards+menstruation+and+menstrual+blood+in+Elizabethan...-a0209577950 and another one at ATTITUDES TO MENSTRUATION IN SEVENTEENTH-CENTURY ENGLAND by Patricia Crawford which can be purchased for $25. Medieval Blood by Bettina Bildhauer - http://litthe.oxfordjournals.org/content/20/4/475.full and on Amazon - looks good too.
