She has gone- she was here but now she is gone. "Is Liz still here?" "No, she's gone". She has been gone- this is past perfect progressive. For something that started in the past and is still gong on. So she left a while ago and has not come back. However you would say it with a time frame. "Is David here?" "No, he's been gone FOR TWO YEARS" or "No, he's been gone since Monday". Let me know if you still don't understand something.

She has gone - the present perfect tense of the verb ''go'', the person was here, but he/she is no longer here. He/She's gone. She has been gone - the present perfect tense of the verb ''to be'' (been), ''gone'' is an adjective here. It's like She is gone but in present perfect tense - She has been gone for some time. I hope this helps :)