Ruling on Making up for the Days of Ramadan for a Valid Reason

The questioner did not clarify the reason for not fasting during the month of Ramadan. However, what is apparent from his question is that she broke her fast due to shortage of water. In any case, if she broke her fast with a Sharʿi excuse (i.e., valid in Islam), then she must make up the (same) number of days that the people fasted. So, if the people fasted for twenty-nine days, she would make up twenty-nine days, and if they fasted for thirty days, she would make up thirty days.