They should have fed it properly.
There is a cat that calls at my dad's every other day and he feeds it. He's even named it Titty Wink's - How do you you tell an 89 year old what he is doing is wrong.
No one ever owns a cat, they are independent creatures and do not seek attention or affection in the same way as dogs and can be quite selective about who they want to interact with. We have a few kicking about our back that come and go but I don't mind. The odd one will come for a stoke and others are more aloof. We live on a cut and they help to keep the vermin down.
No, she's a caring animal lover who fed a cat that had spent time sleeping in her greenhouse. She then took the time to find its owner and returned the cat. The owner is the one you should be aiming your faux outrage at.