Security light on and flashing?

How many keys did she get with the car? If she received two keys then try the other one. The security works with the keys. Then have a chip inside of them. You will have check with a dealer to see if that is the problem for the security system. most of the time they will want to see the car to reset it. It does not mean there could be other problems with the system. I would do a hard system reboot, remove the negative battery cable and hold it to the positive post for 1 minute then reconnect. This will discharge all capacitors so the system can come back online. This guide can help as well.

https://www.2carpros.com/articles/how-to-reset-a-security-system

Please run down this guide and report back.

Your having a problem with an intermittent failure in the Passlock security system. It would require the use of a Tech2 scan tool to even begin to accurately diagnose the problem. I can tell you that the most common failure in these is the sensor in the ignition lock. No guarantees that is actually your problem but I can give you a way to bypass that specific component if your interested.

Here is how you can bypass the sensor.

Go buy a 2.2k (2200 ohm) ohm resistor at an electronics store. Go to radio shack and just get one as close to that as you can. Remove the covers on the steering column and locate three small wires at the lock cylinder. Cut the yellow wire and the orange/black wire or on some vehicles, its the yellow and black wires. Solder the resistor between those wires. Tape it up and put the covers back on and follow this relearn procedure. If this doesn't work you have a wiring problem in the steering column.
30 Minute Re-Learn Procedure
1. Turn ON the ignition, with the engine OFF.
2. Attempt to start the engine, then release the key to ON (vehicle will not start).
3. Observe the SECURITY telltale, after approximately 10 minutes the telltale will turn OFF.
4. Turn OFF the ignition, and wait 5 seconds.
5. Repeat steps 1 through 4 two more times for a total of 3 cycles/30 minutes ( the vehicle is now ready to relearn the Passlock Sensor Data Code and/or passwords on the next ignition switch transition from OFF to CRANK).
Important
The vehicle learns the Passlockà † Sensor Data Code and/or password on the next ignition switch transition from OFF to CRANK. You must turn the ignition OFF before attempting to start the vehicle.
6. Start the engine (the vehicle has now learned the Passlock Sensor Data Code and/or password).
7. With a scan tool, clear any DTCs if desired (history DTCs will self clear after 100 ignition cycles).

Here is a guide that shows you how to reset the security system for your car.

https://www.2carpros.com/articles/how-to-reset-a-security-system

Check out the diagrams (Below)

Please let us know if you need anything else to get the problem fixed.

Cheers