D.,
There is no physiological or psychological reason why an infant must be weaned at one year. I would like to strongly encourage you to consider continuing to nurse her through the winter flu season. Breastfeeding provides immunological protection that can't be replicated in any other way. My neighbor chose to continue nursing past one year through the winter and when her daughter caught the croup, her doctor told her that if the baby had not still been nursing, she would have needed to be hospitalized. With this year's flu pandemic, there is even a stronger reason to continue nursing through the flu season. After that, I would like to suggest gradually weaning, both for your daughter's psychological well-being and your own physical comfort. You can gradually shorten the time she spends at the breast and put other limits on it. Cold turkey would be a shock to both your system and your daughter's.
K. , IBCLC