If this is her first venture into playing music then yes a live person sitting with her exchanging ideas and answering questions is the best way for her to get started.
If she now plays another instrument, and has played with other musicians, there are many how to play bass lessons on the Internet. I found
www.studybass.com to be a good place to start.
Brand new to a musical instrument - the instructor is the way to go.
You mentioned your Middle School has a jazz band. Talk to the director he/she will be able to point you to an instructor, perhaps the school already has an introductory class. Jazz musicians just don't materialize, I bet, the director draws his musicians from classes within the school.
Good luck.