Is it wrong to honk?

I have a confession to make: I honked wrongly yesterday, at the wrong person; someone I should never have honked.

Let me start with my story; a brief one assured.

I was driving to work as usual in the morning, and I stopped at a traffic light (I was the 2nd or third car in line)
On the left was a turning junction.

When the lights were turning green, there was a Proton aeroback which stopped on the left and was trying to jump the queue by cutting into the line.

The cars before me ignored her, and I did so too (remember I totally despise queue-jumpers?)
She did not give up and was swerving her car dangerously towards mine, still insisting on moving into my line.

I was shocked and I HONKED!
At the same time, although reluctantly, I had no choice but to let her in as she was steering her car right and it was so close, it almost hit my head lights.
(after my recent accident, I was cautious and just decided to give in)

When her car took its place in front of mine, I looked up and still reeling from the frustration, I saw something plastered on the back screen of the car which caught my eye, steering my attention away from her car plate number.

There, on the screen was a sticker to indicate that the driver is an invalid/disabled person.

Imagine my horror and shock when I saw that, I felt really guilty at that point!

The story does not end there; while I was feeling guilty, the driver in front was still swerving her car dangerously as she was trying to gain control of her car (I think she's not familiar with the driving).

Fortunately though, she tried to keep to the left and I was not intent to overtake her but as she continued to swerve dangerously, I listened to myself and put on my signal to overtake her.

I kept looking at my rear mirror and there was this nagging guilt inside me.

Was I wrong to honk at her?

I am not trying to justify my actions here; but I really had no idea that she was a disabled person.
Secondly, when a car swerves dangerously towards your own car, even if you seldom honk at people, there is a need to sound the horn to alert the driver that you are on his/her side, right?

I don't know, I felt awful although everyone tells me I am not wrong, and she was in the wrong.

I just felt ever so guilty, and I pray that she will not feel bad/humiliated by the incident.

Ms or Madam, whoever you are, I really did not mean to honk at you, I just hope that you will drive more carefully in the future.