Please forgive me if the following link isn't allowed on WS, but there seems to be some more information there, including a missing person poster.
http://pinfluencer.net/ryuugakusei/
Much of the page is in Japanese, but there is some English, too. Some of what I was able to garner:
She is actually age 30, not 29.
She is a Japanese national.
Their poster lists her heights as 155cm, which would equal 5ft 1in. (We've read 4ft 11in elsewhere)
The last message from her to her friend was at 11:30am on 9/8. Her friend sent her another message around 4:30, but Natsumi didn't respond.
She studied at the Kaplan language school from 5/2-7/22 (according to the missing person poster).
She was living in a shared house.
I think it says she is presumed to have her black backpack, iphone and wallet with her. Her phone was not enabled for calls, just wifi use.
Today, 9/14, from 2:00pm they are asking for volunteers to meet at the Vancouver Public Library to distribute fliers.
Also, here's a short news article on her including a video, however, it's entirely in Japanese.
http://www.fnn-news.com/news/headlines/articles/CONN00336228.html