17 month old refusing- concerned re drying up

[squizita]

I still BF my 18 month old once or twice a day (evening and morning). I know my supply should be v stable now but I still got fullness etc until she was 14 months old!
So, I'm worried because on Friday I missed bedtime, and twice over the weekend she woke thirsty but only wanted water and wouldn't nurse. Last night she flaked out before bedtime milk/bath/teeth and slept though. She woke at 4am and refused breast then went back to sleep.
Is she self weaning?
I know it's unlikely before 2, but I don't want to dry up and leave her high and dry if it's not her true weaning IYSIM.