Why does Isabel pray at the washtub grotto every night after dinner?

Isabel prays that she will become the Queen of May.

“Isabel, are you saying a novena?” asked Esperanza when she found her at the statue, yet again one night. “It seems you have been praying
for at least nine days.”
Isabel got up from her dedication and looked up at Esperanza. “I might be Queen of the May. In two weeks, on May Day, there is a festival at my school and a dance around a pole with colored ribbons. The teacher will choose the best girl student in the third grade to be queen. And right now, I am the only one who has straight As.”
“Then it might be you!” said Esperanza.
“My friends told me that it is usually one of the English speakers that is chosen. The ones who wear nicer dresses. So I’m going to pray every
day.”