Buy it,and just feed it to the BTA.Just hold the damsel with a pair of feeding tongs and stick it right at the anemones mouth.You dont have to kill damsel first.The sting from the BTA will do that.
If the BTA dont accept the damsel,just drop the damsel in your QT and try again the next day.
That anemone is on its way out to the big aquarium in the sky. It is bleached white. Usually it's too late to save them once they get to that point, especially if it's refusing food. Sorry man, that sucks.
I'd still give it another day or 2.And try something different with feeding it.
It will die,if you cant find something it will eat.But if it starts eatting,it can be saved.
It aint easy to turn a bleached anemone around.But it can be done.