She will leave the tower if you loot her safe in Boutique le Chic, claiming it's not safe despite all the guards. If she leaves, you will lose the ability to buy house upgrades. If this happens, the only other option is to let the ghouls invade the tower. After the invasion, Michael Masters will take over the shop, and his shop will sell the house upgrades. If you loot her safe but haven't talked with her (which triggers her leaving and wandering aimlessly around the wastes), you can get her to stay in Tenpenny Tower by killing Roy and his gang.
"Some people don't like living in a boring old suite. Purchase a theme from me and I use all of my design abilities to set your place up in the manner you request. You can choose from the Vault, Raider, Wasteland Explorer, Science, Love Machine or Pre-War Themes."
ps3xbox360pc If she decides to leave Tenpenny Tower, she supposedly heads out to Megaton and can be found outside the main gate causing tremendous graphics lag for some reason. Scaring her away or doing her in instantly removes her effect on performance. [verified]