Can I stop by the cbx to pick up my mother who arrives at the Tijuana airport?

Negative, it would occupy a plane ticket, only with a boarding pass and the Cross border ticket can use it

Hello Alfredo, Cross Border Xpress (CBX) is an exclusive pedestrian bridge for passengers from the Tijuana International Airport to cross from San Diego to Tijuana it is necessary to have a boarding pass that leaves from the Tijuana International Airport.

You can wait for her on the San Diego side, but she alone will have to cross the bridge, clear customs etc. There are people who assist you to buy CBX tickets, they tell you where to go, etc.

Not unless you have a flight at the Tijuana airport!