This is a traditional puzzle about a family that has five daughters. The names of Mary’s father’s five daughters are Cha, Che, Chi, and Cho. In order to fool you into thinking of a fifth name that fits the sequence, the riddle toys around with the names’ patterns.
However, if you closely examine the wording, you’ll notice that the solution is right there in front of you. Given that the first line of the puzzle starts with “Mary’s dad,” Mary must be the fifth daughter.
Mary is the fifth daughter, to answer.