She's still a pullet until she turns one year old.If it's laying eggs it's no longer a pullet, but a hen.
Sources include:
https://www.merriam-webster.com/dictionary/pullet
"a hen of the domestic chicken less than a year old"
https://dictionary.cambridge.org/us/dictionary/english/pullet
"a female chicken that is less than a year old"
This is also consistent with a number of chicken-raising books I have read over the years, and frequent usage on the internet.
I believe it also applies when showing chickens, but I am not positive of that.