I see .. no wonder.
I like her manga but i dunno where i can find her another works. Yes as you said mangago don't have enough her mangas, i'd love to read her doujin or her original story. I mean yeah i read taiyou no sumika and it made me tears. The plot is just so beautiful. I cried you know :'((( so it will be amazing if i can read her another works ! (=・ω・=)
I just remember, if it's her doujin, read "Sudden Evening Rain Hymn" there's 2 vol. But i warned u please don't cry when you read this haha
Then if it's not mangago, try to find on another manga site. I think u can find it :) mind is from the website of the scan group who translate it but i forgot with the link. Also it's been years so idk if its still exist or not
Also i've been thinking that the art is kind of similiar with emi-10 rankai, narusasu dj mangaka. When i see the author name, their name is the same too. Just wondering if they're the same person