For me, it is hard to be 100% accurate as she is sitting down. The dress length is a really good clue as to dating it. I am sticking to my circa 1917-1919 date for her dress. Basing it on the high waist, matching collar and cuffs, and for me a good clue is the round buttons on the high waistband. I tend to think of these larger decorative buttons as more later 'Teens era than 1920s. Not that they did not use buttons in the early 20s, but overall I just get a sense of late 'Teens.
The headband looks fine to me also for circa 1918. She does seem rather artistic and a bit Bohemian. As does the picture on the magazine.
Yes, so late 'Teens to early 20s, I just cannot be 100% sure.