<em>Mi hermana </em><em>te </em><em>da la llave a ti</em>
<em>te </em>is the indirect object pronoun for the second-person singular. An indirect object pronoun <em>(un pronombre de objeto indirecto)</em> is a person that receives the action of a verb indirectly. It tells us<em> to whom</em> or <em>for whom </em>something is done. Therefore, my sister is carrying out an action, that is, <em>she's giving you the key.</em>
