Yuck - I feel for you. It actually sounds like your Dad was already doing a pretty good job of cutting off ties with her. I'm afraid, however, that your text message may have heightened this woman's interest. It might have given her hope that there could be a potential relationship there. I think it might be best to let this woman know that "your Dad's text" was actually from you. This will most likely make her feel guilty for pursuing this further and put an end to her texts. Also, consider this - she didn't have your Father's current contact information. This may have played into his decision to change his number too. He was obviously trying to cut off ties with her.
And if it makes you feel better, ask your Dad about this. It will be an uncomfortable conversation, but it might help you put this to rest. Just don't let it eat away at you.
One helpful web site I have found that let's you both tell your story and probes you to think of additional things is link removed
Also, there are some books out there by Emily Brown and Frank Pittman. Also, askpeggy has some good suggestions. Most of this stuff overlooks our experiences with a parent's infidelity, but it's a good start.
