Madman, a very natural human response - you wont get no stick from me!
Pickle, have a word with your daughters pre-school manager. Make an appointment so they understand the severity of the situation and ask them to allow your daughter to be collected at a certain time or by a close friend or neighbour of yours - only until the situation has calmed down.
If this is affecting your daughter, they have a duty of care to ask the other woman to refrain from speaking to you or having any contact with you while on pre-school property.
Worse case senario - speak to the police.
Try and collect your daughter when they is many other people around so that you always have witnesess. If thats not possibl, buy a hand held voice recorder and have it in your pocket so that you can grab it when you need to. Warn her thou, if she starts, that you are recording her so that you can take it to the police and get her arrested for harrasment.
Good luck, last possible senario, move Pre-schools if it gets too much - not a great idea i know, but it would stop all bad feelings and that does also rub off on your daughter.
Flower xx