You should factor in many things before you decide to take her back on. Will you be prepared to be dumped at a moments notice again.
You might also want to calculate an increase in price, how will you do this. Think of the various incidents that would be factored into this.
1. The £100 car repair of the damage that you caused. If she's only every 8 weeks at an increase of £5 it's gonna take you at least 3 years to get your money back.
2. Cleaning the previous window cleaners soap off and the dirty sills. That's at least double first clean.
3. Ink and paper on the note that you posted through her door, ok she never asked for it but she must of known how you would react to the trad volvo based ladder monkey with orange trainers, it's like red rag to a bull.
4 The time you've spent writing above said note and also time spent speaking about her on this forum. Seeing as all window cleaners earn on average £1000/hr thats gonna take a few cleans to work off unless you are a very fast typist and therefor not wasted too much time.
5. Dignity, this is really priceless however seeing as you once drove around in a volvo estate that might have already gone before the incident.
I'm sure you will consider all of the above and say Yes Mrs N ill be round in December and the price is £20.
Simon.