Ok first off STOP hitting her! She on the defensive because she knows the routine, she takes something of yours, she knows it will be confiscated, she wants to hang on to it, but knows she'll get a smack so she wants to get the first 'attack' in there.

I know its hard when she has something she shouldn't but relax, the chase and the struggle to get it back are the rewards for taking the items. You need to offer her something very tasty in return for the item. You aren't rewarding her stealing, you're rewarding her giving up the item.

So if she takes something, have some very tasty food, it has to be high reward, so meat, cheese, or something really smelly, fishy or liver. Drop some bits in front of her, let her eat them, then try to offer from your hand. Say a cue, such as 'Mine' and attempt to remove the item whilst she its eating the treats from your hand.

The most important thing here is that you don't get into a confrontation with her. She's already shown, she is prepared to snack at you, so you don't want to make her threatned and feel she has to up the aggression

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