What?! No, it doesn't! ಠ_ಠ
Why on Earth would the Silk Scarf increase the power of Normal type moves if they were being changed to Fairy type moves by Pixilate? They're not Normal type moves anymore!
Here are two calculations conducted using the exact same Pokémon, the only difference between the two is that in the first calculation Sylveon is holding a Silk Scarf, while in the second calculation Sylveon is holding a Pixie Plate.
Silk Scarf:
0 SpA Pixilate Sylveon Hyper Voice vs. 4 HP / 0 SpD Latios: 254-300 (84.1 - 99.3%) -- guaranteed 2HKO
(254, 258, 260, 264, 266, 270, 272, 276, 278, 282, 284, 288, 290, 294, 296, 300)
Pixie Plate:
0 SpA Pixie Plate Pixilate Sylveon Hyper Voice vs. 4 HP / 0 SpD Latios: 302-356 (100 - 117.8%) -- guaranteed OHKO
(302, 306, 308, 312, 314, 320, 324, 326, 330, 332, 338, 342, 344, 348, 350, 356)
Source