I thought I had better photos of her but can't find them. She is so much larger than this photo shows. The comb has just started turning a bit red in the last few days.
Pullets are supposed to start turning red in the comb after 4 months old. It's normal and means they are maturing. Eggs are only about a month or so away.
Your picture looks like an 8 to 10 week old cockeral vs. a 4 month old pullet. At 4 months a chicken is pretty much fully grown, but look at that size difference between your chick and the chicken next to it. If the picture is truly that deceiving in size and the chicken is 4 months then its a pullet.
It's just a play in the angle of the photo. She is one of the three largest girls I have. They were all 2 days old when I received them so I know she's 17 weeks old. That's also why I said she is much larger than the picture shows.