Hoshizaki Suzuno/Star Broché from Henshin Heroine ga Aku ni Ochita Hi, a manga series by Group Gohan Oomori.
I'm not sure if it's actually Broché or Brooch because the only two chapters that got translated has different names for her transformed state. I'll stick with Broché though.
Description
Star Broché - starbroche, magical girl, 1girl, solo, blonde hair, very long hair, low twintails, hair bow, light yellow eyes, earrings, choker, bowtie, white shirt, puffy short sleeves, gloves, back bow, layered skirt, red skirt, orange skirt, white knee boots,
Hoshizaki Suzuno - hoshizakisuzuno, 1girl, solo, blonde hair, medium hair, low ponytail, dark yellow eyes, white shirt, short sleeves, collared shirt, red bowtie, blue cardigan vest,, blue pleated skirt, black knee socks, brown loafers,