I know she has an iPhone because her text tones are the exact same as mine.
My phone is always on silent (almost always, to be accurate but still) and when people text it goes "buzz, buzz."
And when someone texts the girl upstairs, her phone also goes "buzz, buzz."
Which means sometimes I'll hear her phone alert and I'll check mine for texts. I don't know if she has hers on a table or on the floor or something else that vibrations travel through but her texts sound just like mine when I have my phone on the couch beside me: slightly muffled.
I've even been using my phone, on a game or something, clearly seeing that no text has come through but hearing the "buzz, buzz" will make me check.
Like, hello Pavlov, may I have my dinner now?