Idk if links are allowed here, but look up Security bar or Kick bars for doors. Amazon has some from 15 usd to 40 usd. Shouldn’t be visible as it goes under the door knob like the way one might use a chair. It still might let her open it far enough for a better look into the room but she’s gonna have to fight a door secured with a metal bar to actually get in. Works on most carpeted and smooth floors.