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Well, I suppose that she could move, in the bankruptcy court, that her informal claim be deemed to be an effective claim or, alternatively that she be allowed to file a late claim (because she was not properly served), and that the settlement agreement be set aside. This would be a long shot at best so she definitely would need an attorney to handle it for her.
Another angle would be to file an adversary case for damages against her ex husband for intentionally giving a wrong address for her.
Other than that, I have no other suggestions to make.