Is there an indoor range where you can rent something with ordinary open sights, like a .22? Explain to her how she would have to focus on THREE different objects at different distances. A peep sight eliminates half of that workload.
It's important to become an expert with iron sights, if just to gain confidence in yourself and your weapon. The Marines still emphasize that, but the Army dropped that concept ages ago, just going for pop-up silhouettes, rather than paper bulls eyes. You've got to learn confidence in your rifle and your basic skills. Once you know you can make certain shots with just the peep sights, you know you're going to clean up with some advanced sighting equipment. You'll also be able to fall back to iron sights if you ever have to with nothing more than a sense of annoyance.
She understands “regular” iron sights PERFECTLY! But I just know that before she gets the hang of peeps she’s going to wonder WHO in their right mind invented them! :-) You have pointed out some good things about them though that I’ll explain to her. I’m pretty sure that she’ll do like most of us and gain a true appreciation for peep sights. I’ll keep you posted! Thanks!