Change your number
Try not to have any contact with her if at all possible. Block her on facebook. Don't respond to emails. Eventually she will probably get the message and even if she doesn't, hopefully you will not have to know about it.<br />
I think the #1 thing is do not fuel her fire. Don't get mean and bicker back and forth and increase the drama factor. Don't play nice and make her think she has a chance to get you back.
Tell her you now like boys.
I changed my phone number.