You'd really be surprised. A lot of times we can tell by the way you type, for instance:
* using a lot of punctuation, or none at all
* Always capitalizing the proper words, or never capitalizing anything, or capitalizing Random words
* telling certain jokes and stories, or telling them a certain way (writing it all out at once vs. sending each line of story piece by piece)
* using the same font/font color
* tipping for certain things or in certain numbers (tipping 39 to make a 439 countdown an even 400, always tipping 1 then 2 then 3 then 4, etc.)
* misspelling certain words, or using unusual words fairly often
* certain personality quirks (being argumentative, saying hello to everyone in the room, using lots of emotes, telling life stories, talking about video games, etc.)
These can all be an obvious sign to a model that you are the same person she has seen before.
We don't get any information about members unless you post it on your own profile-- and I'm going to be honest, most of us never bother to check member profiles. We are never given your name, your location, your birthday, your credit card info, or anything like that...unless you provide it for us. So she was eitehr guessing, or another premium member knows your secret and tattled on you!