Our "financial model" is a fiction and the next investor will see it

I built our model in two weekends from a YC SAFE doc and a Google Sheets template I copied from a blog post. Numbers project us to $5M ARR in 18 months. None of the assumptions are defended. I just needed something to send.

We got 3 angels in on it. Now a real VC is asking questions and I'm panicking. They wanted unit economics by cohort. They wanted CAC payback by channel. I don't even track CAC.

I don't know if I should rebuild the model honestly (which makes us look much smaller) or keep the fiction alive and hope I can ship to those numbers. What do you do when the deck and reality don't match?