Girlfriend entering U.S. just to drive to Mexico — will this be an issue at LAX?

Hello everyone.

I have a question regarding travel through the USA.
I am from California and will go visit family down in Mexico. While I have no problems as a U.S. citizen, my girlfriend from Germany will also be coming over on a separate flight. She will be landing in LAX where I will pick her up and drive south to Mexico where we will stay for the duration of her trip before returning to Germany through LAX.

Her main worry is the fact that she is entering, but not staying in the USA and therefore not being able to present an address of where she will be staying or any proof of her traveling further to Mexico, since no other flight ticket as I'll be picking her up by car. Will this present an issue? Does anyone else had to deal with something similar?

We are literally only flying to LAX because it is the cheapest way to go to Baja California.

Any insights will be greatly appreciate it. Thank you.