Okay, MN what do I say to dd(7yo) about tooth fairy?

[SkateLife]

Dd lost a tooth today. She is over the moon that her tooth fairy is visiting her. She's written a letter explaining how she lost it.
Then at bed time she whispered to me "Pinky promise it's not you mummy?"
I replied "shhhh baby go to sleep."
Now I'm wondering if I should write back from the fairy saying that she's old enough now for mummy to take over the tooth fairy duties.
I remember finding out that the tooth fairy wasn't real, the fact my parents had lied, when all my friends had said it wasn't real.
Should I keep the fantasy alive, tell the truth or let her down gently in a letter. I'm torn, would appreciate some advice.

DS (10) knows FC isn't real, not sure about the tooth fairy. DD1 (7) definitely believes in toothfairy

Thanks. But I still don't know what to write

Don't write anything.

You are overthinking this, she asked you to promise, you gently refused. The conversation has happened, put the money under a pillow and await a cue from her