Patria alludes to the "crown of thorns" to describe her torment in the days and weeks after her sisters, husband, and son are rounded up by the Trujillo's police force, the SIM. "Crazy with grief", she has moved to her mother's house. Although she gradually recovers some measure of sanity, she cannot rid her mind of pictures of what has happened and what she imagines is still happening. Patria envisions
"the SIM approaching...the throng of men at the door...the stomping, the running, the yelling...the house burning...tiny cells with very little air and no light...hands intrusive and ugly in their threats...the crack of bones breaking...the thud of a body collapsing...moans, screams, desperate cries".
Patria likens her mental suffering to the suffering of Christ, her own "crown of thorns...woven with thoughts of (her) boy". She also uses a number of other allusions to Christ's Passion and Resurrection - working through her grief until her "cross became bearable", enduring another "crucifixion" when the SIM comes for Mate, and awaiting redemption for those imprisoned with the assurance that "on the third day (Christ) rose again" (Chapter 10).
I am not familiar with the book you are reading but an allusion to a "crown of thorns" is usually an allusion to the Crucifixion of Jesus Christ. When Christ was on the cross, a crown of thorns, was put on his head so that the thorns would stick into his head. The crown of thorns itself was symbolic of the crown of olive leaves worn by the Roman Emperors since Christ was being executed for his supposed claim of being the king of the Jews. When one alludes to a "crown of thorns" they are usually referring to severe and painful undeserved punishment just as Jesus punishment was undeserved.
This quote is on page 201 of my book. It may be more helpful to tell you that it is on the page after chapter 10 Patria. The Crown of thorns is originally from Matthew 27:29. it is one of the instruments of passion used in the events and the actual crucifixion of Jesus Christ. I hope this helps.:)