My 4 RIR girls started laying around the 22-24 week mark. That being said, it's Winter here so that may have held them off a little.
Whilst some chickens do lay earlier, generally most are at least 18 weeks old. Your girl certainly looks red, but I think her comb and wattles could still plump out a bit.
You never know, she might surprise us all and lay tonight, but my best bet would be another month or so!
You could certainly start getting some nest boxes ready for her to look at though. They like to investigate the boxes, hop in and out and flick straw everywhere. If she starts doing that, and squatting, your eggs won't be far away.
Good luck!
- Krista