When it follows "て(te-form)", this いる is called one of the helping verbs grammatically, and generally means either of the following. 1) an action in progress (= progressive in Eng) 2) a past event that is connected with the present (present perfect in Eng) In this sentence, both いる indicate 2. She's kept the state that she knows where he has lived. Or perhaps the latter might be 1; he is living now. It depends on a context like English.

しっている iru ＝ know しっていない inai ＝ dont know

しっている = I know