Sometimes after they have been laying, they get nicer. You can hope for that. Does look like a pullet to me - maybe she has pms - and an egg or two will straighten out her hormones
I've just been through this with mine, 4 of 6 are roosters! I think you have a pullet about to lay if the comb and wattle have only just got bigger and redder. I used the tips on this site to confirm my roosters, the neck (hackle) feathers were the give away and the folks here agreed. They are younger than yours though. Thankfully my family are on farms so they had somewhere to go
This is the photo that raised suspicion
At only 12 weeks old it's obvious that there are 3 roosters and a pullet in the picture. Yours are twice that age.
Hope that helps!!