How does a person disable their defective car alarm?

Our teen daughter was given a 1997 Toyota Avalon by her grandparents. In the last week the factory installed alarm has disabled the car and sounded the horn and lights without notice on three occasions while she was trying to start it.

Is there a way to permanently disable the alarm? Her car is not exactly high- risk for theft anymore.
I am concerned that she will be locked out of her car and put in a dangerous situation.

Any suggestions will be appreciated.