Twenty-one or over: the age rule for everyone
Every guest, every therapist and anyone else in the room must be twenty-one or over. At the door she may want to see an ID with your photo on it.
This site has one age rule, and it has no exceptions. Everyone must be twenty-one or over. That includes you, any second guest, and anyone else who is in the room while she is there.
At the door
She may ask to see a document with your photo and your date of birth, such as a passport or an ID card. She checks it once, and it is back in your hand a moment later. Nobody copies it, photographs it or writes it down.
If there is a doubt
If she cannot be sure that someone in the room is twenty-one or over, she leaves before the session starts. This is not a judgement of anyone. It is simply the rule, and it protects everyone.
Reading dates of birth
A document from another country may write the date of birth in a different order: day first, month first, or year first. If that happens, the month in letters, or the year, usually makes it clear. The guide to hours and dates explains the three orders. The age page has the full rule in formal language.