It is hard for me to understand what MAC thinks a beauty powder is, as some of them have no color and no shimmer, while others look as high metallic blushes - and Alpha Girl is a satin blush on my NC20 skin. Moreover, they don't possess any upgraded performances or strengths and should be taken as is: as pressed powders.
Alpha Girl is a warm toned medium pink with a soft, subtle satin sheen. It is very thin, but for a natural look, it doesn't need much of building up. It wears well for 7 hours on my combination skin before it starts to fade. The texture is silky smooth and there is no excess powder. The shade reminds me of NARS Orgasm, despite being more of a petal pink, when compared side-by-side. On me, it translates as a natural flush with no metallic sheen. I find it to be perfect for no makeup looks. I can't use it as a highlighter, as like some other MAC Beauty Powders. It feels like the only real use of it would be as a blush.
While the color is not hard to finger-swatch, when swatching on my wrist almost no color got translated (see pictures). Still, I have no problems with the application using brushes (MAC 169 and Sephora Pro 59), and two brush swirls were enough to translate the color to my cheeks (see photos).
The good thing about this particular shade of Beauty Powder is the price. If you're into warm toned, coral-looking pinks, and have light or medium light skintone, this would be a good investment as the size is nearly double the size (10 g vs. 6 g) of their regular blushes (25 vs. 29 euros).