I would stop directly lying to her. Be more like a politician!
What we did with our DC was, if they asked directly, to evade the answer without actually lying, e.g. answering questions with "that's an interesting question, what do you think?" And then "really?! And do your friends think that too?" and take the first possible opportunity to change the subject or leave the room!
Neither pushed it enough for us to have to tell them directly, and they worked it out by themselves over time without any drama.
Now at secondary, they still get stockings and we still pretend Father Christmas comes, but it's just a fun game we all play. There's an unspoken agreement that if you say FC isn't real, the stocking might not appear!
I think adults need to remember that DC play imaginary games all the time e.g. they they're a dinosaur or an astronaut or a bug or whatever. We don't need to tell them they're not really that thing, not do we need to directly lie to them that they are, in order for them to enjoy it.
Father Christmas is a fun make believe game we all play, but adults forget about how to play make believe and get far too invested in the lie IMO and then we find ourselves in tight corners!
I did with the tooth fairy, which DD realised wasn't real at a much younger age, and I before I'd worked out how to avoid questions like a politician. She asked me directly. I asked her if she really, really wanted to know as you can't take it back once you know. (Or so I thought!)
She said she did, and so I told her the truth, that the tooth fairy was us. She was absolutely distraught, it turns out she wasn't ready to hear it wasn't real. I felt so bad I backtracked and said I'd got it wrong, and actually money did appear from somewhere so it probably did exist. She went on believing in the tooth fairy for a while after that, she obviously just really wanted to!