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I am sorry to hear about this concern.
Well, you can still work with your vet on trying other forms of behavioral modifying including drugs or pheromone therapy like Feliway spray or plug-in.
Is she too old? No
However, most vets are reluctant to do the surgery at this age since it is a bit more invasive, can be quite painful and involved.
You'll have to really have a good discussion with your vet about the surgery and it might be worth only considering having a vet do it that has laser surgery.
It is a controversial procedure already, but some vets will still agree to do it if the alternative is euthanasia or when a family member is immunocompromised and at risk for injury from any type of scratch.
Hope that information helps