They most likely did. Roseluck is a background pony in the show and I haven't been the only person to vector her cutie mark. In fact, their's has more rounded areas than this one as well as line thicknesses that are more uneven.
The thing is she's a known thief, most of the deviations on her page are from someone else, including pictures of someone's cat that she is claiming as her own. Yours was the first Roseluck cutie mark I pulled up dA, which is why I commented. However if you noticed different line thicknesses, it's most likely it isn't yours that she has stolen.
Can't you make a cutie mark for my pony? He's Fire Blaze...watch a pic of him on my gallery. Maybe you could make a cutie mark..like a lightnign with fire, fire, a cloud with fire, or a lightnign with a cloud with fire...something cool with fire...please?