Predator stress does have an impact. Sometimes they may not lay from stress for a while. Or it can cause little blood or meat spots in the eggs.
Speaking of hidden nest.... well one thing is you would notice 1 bird missing from the group for a period of time, that would likely be a layer. Well, my BO went missing but with zero signs of predation. :/ Told my family to look out for her to randomly show up, and she did yesterday!! But quickly disappeared again. So she IS sitting on a nest somewhere... and 14 inches of rain expected over the next 2 days!

Glad she isn't dead and hope to see some chicks.

(even though it isn't the preferred time of year)
Also, I'm of the camp that thinks natural lighting is better for a bird then extra light adds stress. Though there are some better methods, for example not leaving the light on ALL night and adding it in the morning hours. Personally, what comes natural is good enough as I am not trying to turn a profit. But I do understand wanting to get eggs sooner!
There are some sign if her chickens are even close. The combs will redden up quite a bit. And many will squat when you quickly put your hand over their back. Mine are usually within about 1 month or less to start once I see these signs. Putting fake eggs in the nesting boxes allows them to see where they SHOULD lay and that others think it's safe to lay there. They will practice moving the egg around and adjusting the nest, it's really cute! They usually show zero interest in the box and egg until they are getting close. Fake eggs are quite effective for me.
Are you and your friend using the same feed? A higher protein feed like flock raiser with oyster shell on the side is good. If you start layer too soon it can have long term side effects on non layers as the calcium is too much and CAN cause kidney issues. Layer is lower in protein and the bare minimum amount to keep birds viable while laying. And if using layer it is still advisable to have oyster shell on the side. Good luck!