Brian, I am 53years old, so what I am going to tell you, please listen. Don't text back, ever. Change your number and keep only your family and best friends posted of your new number. Don't even text her and tell her you have moved on. No contact what so ever.

It's going to be a problem for quite some time to come, and I suggest you 1) Tell your soon-to-be-fianće about the situation. Failure to be forthright about something that will eventually involve her (and it will) is a violation of trust that you do NOT want to start with in a serious relationship. And, 2) Get a restraining order now. Don't wait. Let her know that you are not going to play into her games from the very outset. This provides you with a means to "follow-through" should she continue her harassment, and demonstrates to your girl that you are committed only to her – thus defusing a volatile situation with her before it even becomes an issue. Hope this helps, from a retired military JAG.