Euthanasing a healthy elephant would certainly be immoral and entirely unnecessary.
Donating her to the SPCA gave them a huge PR boost, lots of extra donation dollars and her new circus owners a significant tax write-off.
Had she been worked in Protected Contact this thread would not be here.
In my own humble opinion I can't see any problem with leaving her at Franklin - providing Helen's heirs want her, of course.
She has a magnificent, purpose built facility there, she can be handled PC quite safely, she is used to being on her own - indeed she may now be incompatible with other elephants. There would be no benefit in shipping her all the way to America to find that she would have been better off left in NZ. She is over 30 years old so, despite what the "experts" from the AR movement tell us, she really doesn't have too many years left.
One person's opinion.