Anime where teenage girl's growth has stopped
To my knowledge, it is as someone already mentioned, The Friendly Winter. 


  A 19 year old girl with a rare growth disorder that leaves her in the body of a small child meets a boy with a mental disorder, who has the mind of a small boy in a 17 year old's body. A Friendly Winter shares with us the endearing story of their day-to-day lives, joys and tribulations.




You might have mistakenly remembered it as an anime because it is fully coloured. It is actually a Korean Webtoon. Her hair is close enough to be misremembered as pink.

In the end,


  she is proven a capable business woman who runs a children's apparel fashion line.