@ToonLink You are right. I'll not give up and keep the feeding long term. At least, she might not respond at all to whistling/calling but she is like a clock for her visit for food. Around 1am, she seats in front of the door and wait. When I open the door, she run like 8 meters away. I leave the food, and then I have to close back the door. Only then, she come and eat.
She really has a maximum security protocol with humans.