Why did Esperanza's heart ache for Isabel?

Isabel is Juan and Josefina's daughter teaches Esperanza how to take care of the babies and do chores. She is younger than Esperanza but has a great deal of maturity and knowledge about living in the camp. Isabel's dream is to go to school so she can learn English. She loves hearing stories about Esperanza's privileged life in Mexico. Esperanza wants Isabel to realise her dreams.