The following is an extract taken from an Italian student's piece of English homework before I corrected it.
Also Mr Amos’s girlfriend, Sabina, arrives to the restaurant, and she assisted to David’s [Mr Amos] love confession to Anna. Then the waiter began singing his love to Anna. A fight broke out and Anna decided to leave the restaurant.
What's bothering me is the phrase: ... she assisted to David's love confession to Anna, which I corrected as
1) ... she listened as David confessed his love to Anna
2) ... she listened to David's confession of love for Anna
But could I have left it as David's love confession?
3) ... she listened to David's love confession for Anna
The phrase to confess one's love is idiomatic and grammatical, but what about "one's love confession"? I can't explain why love confession is inappropriate (or ungrammatical).
Google is of no help, and Google Books gives a lot of false positives, which however confirm that love confession is at least, an unusual expression.
Examples of "his love confession" using Google's search engine. These are taken from the first three pages. Although the phrase "his love confession" appears to be common, it's clear the following are not written by native speakers.
A top Japanese star confesses his love for Kara's Nicole? On the recent episode of Japanese music show "Music Station" Nicole and Japanese rock band member from L'Arc~en~Ciel share an incident where Nicole receives his "love confession."
He was completely frustrated, this was all Takao's fault with his stupid love confession.
In a dream, Banri remembers that after his love confession to Linda, she agreed to tell him her response the following night on the bridge where Banri would have his accident.
Cho kyuhyun loved Seo Joo-hyun so much and started his own love confession to Seo Joo-hyun. He started giving lots of presents to Seo Joo-hyun which make Seo Joo-hyun's life miserable.
Ji Hyun Woo Shares His Thoughts For First Time After His Sudden Love Confession
The excerpt is from a student's summary of a short American story. The original author does not use the word confession or vow in any form, shape or size. It is the only the student's attempt (and quite a good one too IMO) to summarise the episode at the restaurant table. My query is not whether there is a better way to rephrase love confession, but as to whether it is idiomatic, acceptable and easily understood. I believe it is not idiomatic, but I can't explain why it is not "acceptable".