It is from the book "We need to talk about Kevin" written by Lionel Shriver. English IS her mother tongue. The novel even won Orange prize, which is awarded only to novels written in English, by female author.
Ms Shriver likes to use many strange metaphors, some aptly made, some not. The book is full of such passages, and some of them are posted on this forum. I asked for help in their translation, and I was hugely relieved to find out that many native speakers didn't get them at all. I thought it was just me. Nevertheless, I must say it is a great book, despite its sometimes strange discourse and vocabulary, and I recommend it.
Thank you all for helping me! I am sure I'll post some more puzzles for you before I finish translating it.
Lucrezia