She might need a youth clipper card
https://www.clippercard.com/ClipperWeb/s...
Call BART customer service if you want to clarify things. As far as i know, if she uses a regular clipper card, she probably wont get a discount. The regular card is for adults, so its based on the regular price.
edit: so then she should already get the discount. The discount should have been calculated already, according to that webpage.
Youth Clipper Card. Youths aged 5 and older are eligible for a free Youth Clipper card. With a Youth Clipper card, you can receive discounts on monthly passes, .
Senior Clipper Card. Adults 65 and over are eligible for a free Senior Clipper card. With a Senior Clipper card, you can receive discounts on monthly passes, .
Clipper Discounts. Clipper offers discount cards for youths and seniors. Customers with disabilities may also receive a discount card through the Regional .