“When your aunt picks up the rental vehicle, she should ask the rental agent whether travel to Mexico is allowed. Some locations allow travel to Mexico, but only if you make your intentions known. Bear in mind that Dollar also has the following requirements and restrictions:
Failing to inform Dollar about your Mexico travel plans or taking the car across the border without proper approval will invalidate any car insurance you have through Dollar.
If Dollar does not allow travel to Mexico, you can look into other rental car companies or consider choosing a different destination for your trip.