The Last Horcrux/Bedroom/Cast An Occlumency Charm
Your first priority is to keep your true identity hidden. Reaching up with your wand, you point it toward your temple and cast a rare but powerful obscuring enchantment on yourself.
"Psyche Obfuscatus" you say, and the depths of your mind are hidden. Now, any Legimens attempting to discern your true thoughts will see a layer of false ones - a mask of girlish triviality that a child such as Emily might be expected to think.
There is one problem though. The girl. Just as you can rifle through her memories as easily as you could steal from her bedchamber, she too will be able to see your memories. For now, she seems too cowed and frightened to look there, and indeed, many of your memories scare even you. Eventually though, eventually she will be tempted to look, and you cannot obscure your own mind from the possession vessel itself. Your patterns are too intimately intertwined for that, and it will only become harder the longer you dwell in this vessel.
No, the girl must remain loyal, even after you are done with her flesh. She can become one of your servants, or perhaps...
Now that you have a wand and some protection, you decide on your next course of action:
Or do you need to talk to your allies next?