2000 Honda Accord alarm malfunctions now car won't shift gears?!

My brothers car alarm often doesn't disarm when you unlock it with the key fob and will set off the alarm when you open the door. We still can't figure out how to turn it off it just seems to go off randomly or not all all until you disconnect the battery. So my mom is stuck in the car right now, the alarm just went off several times when exiting the car, then finally quit so she gets back in the car ten minutes later, starts it and can't put it into gear! I told her to try disconnecting the battery, so she's doing that and going to let it sit, but if that doesn't work what can she do?!

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