It looks like she's wearing her collar close against her nape, or at any rate not in the super-low position geisha use. Therefore, the pattern modifications specific to hikizuri aren't something you even need to worry about.
You can just make an extra-long standard kimono with VERY long sleeves and add a padded hem.
I'm guessing from the fact that you know the term "hikizuri" that you're pretty familiar with kimono in general and may know the basic rectangle-patterning way to sew one. If you don't, this
is a good guide with links to other resources if you get stuck.