My sister made some croissants for me but I don't want to eat them.
Why don't you want to eat the croissants your sister made for you?
I don't trust them, she might have poisoned them.
I'm sure your sister didn't poison the croissants she made for you. You may not like her, but there's no reason to suspect that she's trying to kill you.
I don't trust her and I won't eat anything she makes for me.
I'm sure your sister is not trying to kill you, but if you don't get along with her and don't want to eat what she gives you, that's your right. You don't need to feel bad about it, it's fine.