My RIR got a bigger and more red comb a couple weeks before she started to lay. It got noticeably floppy a day or two after she started. Yours looks pretty floppy (though I think leghorns are known for their big combs, maybe?) so I’d guess an egg is soon! Have you done a pelvic check? Doing so on my RIR allowed me to know that she was likely within a couple days of laying (and I was right!).