She was a side character in Strike Witches: Maidens in the Sky. This manga has since been retconned, and no longer considered canon.
She is first seen training at the Yokosuka base under the guidance of Takei Junko. During one of her training missions, she crashed in front of Miyafuji Yoshika due to a striker unit malfunction. Yoshika brought Tomoko to her family clinic and healed her with the help of her grandmother. Later, Yoshika accompanied Tomoko back at Yokosuka base.
These series of events did not occur in the anime which was aired shortly later, thus it is non-canon.