It would seem rather unfair to this guest if you would try and make other hosts avoid her especially because she hasn't done much wrong in this situation apart from owing you money due to a double refund.
Regarding the refund I would contact ABB and they would see the double refund in their system and then correct the mistake or perhaps they are in the midst of trying to resolve the matter as we speak. They might even have an open case already for all we know -even though it seems yo've been waiting too long.
This community isn't really for "warning other hosts" - reviews can be left for other hosts to rely on - but I totally get why you want your money back but I think you ought to contact ABB .
Best of luck