The probability that at least one student in a class of 15 gets all 24 questions wrong on a 5-option multiple choice test is about 6.8%. Such an occurrence isn't particularly remarkable.
Madison says : "Irene, you were near me every time I used my powers. You have powers, not me" and we can see one flashback about the cantina.
However, the first time Madison discovered her powers by guessing all the cards, she was alone in her room : Irene was elsewhere at that time.