I'm glad you're OK and Mom is doing well.
However, in all my 53 years of life and 37 years of driving, I've not found a GOOD reason to use the horn on my automobile.
My suggestion, disconnect the thing, they usually are used for all the wrong reasons. The guy probably had no idea he nearly hit your Moms car and probably thought the opposite when she honked. End result....raging thicknecked dickhead who probably has a problem with Poly Sci Professors...

Be safe and carry regardless of where you're going. If your gonna be drinking, do it at home.