Hi, apologies for the late response with this -- I don't get onto dA much these days! Feel free to use it as reference, just please be sure to link the original photo in your description Can't wait to see the finished product!
I enjoy this piece alot. As an illustrator, I feel I'm only good for judging compositions. xD I take awful photographs. This has good composition and the red flowers are a nice touch to the white lace. The make up is alot more subdued as far as this style of make up is concerned,very minimal and while that's not my preferred method, your sis was precise and was smart about where she added the lines.
My 5 year-old wants to be a Sugar Skull for Halloween...dunno if I can come close to matching your sister's artistic talent, but I am going to try and recreate this make-up for my daughter's costume. She's going to be SO excited, I can't wait to see how she turns out!!
She bought a black headband (not a full cloth one, but one that you just slide onto your head) and glued the lace for the veil to the underside of the headband. She glued silk flowers on the front and back of the headband to hide it.
She used costume makeup from one of the kits that they sell at the Spirit Halloween store.. She also said she used a setting powder which helps to keep it even looking. She used little rhinestones that they sell for decorating your nails with as the colored dots around her eyes. She used red lipstick, and blended black eyeliner in the corners of her mouth to make it darker. Hope this helps!