AMexico City: Passport book or Passport card for air travel within Mexico
Hi Alyssa, If your flight becomes Domestic, your friend may not need more than her card, but it depends on airline specific rules, it will be better if you check documents area directly on the web site of your airline.
AOaxaca: Oaxaca City ADO bus terminal
Hi Mia, it has it: Oaxaca, Oax (to Puerto Escondido, maybe) I just checked on https://www.ado.com.mx/ado2/#/
AMexico City: Four days in Mexico City - need suggestions
You have to go to to Coyoacán, eat street quesadillas and drink: champurrado or atole, if you had only chance to check one day, those will be my choice