Jean,
Good news, stop beeing sad!
I also googled for Sister Edeltrud Koch and found the obituary notice, but saw it came from southern Germany. Koch is a very common name, so I called the benedictines in Steinfeld and asked for her. Sister Gracia there told me that Sister Edeltrud Koch still lives there beeing the oldest of the sisters. She remembers a lot but doesn’t hear well, so she said speaking to Sister Edeltrud on phone was not recommended. Sister Gracia asked to send a letter and she is shure that Sister Edeltrud will be happy to receive it and to answer it.
You will find her address on the website of the cloister. If you want, you can write the letter as message to me, I would translate it and return it so you could send it yourself, if you do not want to ask your german friends.
Christoph