If I don't use eye primer, eyeshadows do not show up well AT ALL on my eyelid. And I can't fault every shadow out there - it's something to do with my skin type or tone, I suppose. Sure, some would show up better than others, but generally speaking, they just don't stick to my lid well without a primer. I don't know Christine's skin type so I can't say whether her eye looks are due to issues similar to mine or whether they're the result of the way she applies the products. But I can swatch a shadow on my arm and have it show up well, and then when I go to put it on my eyelid, it's barely there - soft and I can't build intensity. But if I use a primer and give it something to adhere to, the intensity is magnified. I don't consider it cheating - I just think it's what I need to do to assess the actual potential of the product. So - if you've never experienced that problem - you're a lucky duck! I just know for me, I could never and would never even think of applying a shadow without primer for that reason. Prevention of fading and creasing is an added bonus, but primarily I use it to give the shadow something to stick to so I can get decent intensity.
I've just noticed that a lot of her looks are...subtle. So it makes me wonder if she has the same "issue" as me, but for some reason prefers subtle looks or feels it's only "right" to show the shadows without primer. Because as Shars pointed out, the arm swatches often look great, and then you look at the eye and think...where's the pigment? That's exactly what would happen to me if I didn't use primer. As long as she's consistent across all products, I guess that's good. But if it were me - knowing my eyelids - I'd still use primer! Just my two cents!