True Names are referred to in quite a few different places in the novels. Pretty sure Bob says at one or two points that the True Name of a mortal changes over time. If you're looking for something in the system to kind of reflect this, you might use the character's Aspects as a rough gauge of how much their true name has changed since dad knew her. Changing ones legal name wouldn't hurt but really a True Name is who you are, not what you're called. Fake identities are sort of off as a way around it too, for the same reason.
Unfortunately I think a "Rebirth" spell would be a transformation. The results probably wouldn't be pretty. But over time, it could happen on it's own. Her best bet is probably to find a way to block him off from using it. Making him forget (mind magic, but one of the fae could do it without all that pesky Lawbreaker stuff... which makes this an adventure seed), find any other supernatural allies he might have and make sure they can't or won't cross her (another seed), gain blood and/or hair from him for use in a deterrent of some sort (not as good as a seed but still something), or have a scene with him where he's fully informed of exactly what a death curse is, what it's capable of and letting him know he's in the crosshairs for hers. I guess technically he wouldn't need allies if he already had access to a common ritual that wasn't too widely known to be of use, she might need to watch for that if she goes the allies route.
Basically as a GM your best bet is to turn this into an adventure or at least a side quest. Really one of the best things you can do for a player is to take elements of the story they give you and acknowledge them by incorporating them into the tale you're spinning.