@tenrx
Do you mean that it started with simple jealousy? Or was it the line, "I was just not brave enough"?
The jealousy issue was resolved immediately after an outburst followed by apologies from each of them.
"Bravery" has something to do with moving on and breaking up and not trying to hang onto the relationship.
I probably had misinterpreted page 4 to mean that they never talked, but it seems like it only meant that they didn't contact each other during the holidays. The library panel meant that there was some distance between them already but not that it implied that they never spoke a word to each other.
What really made them drift apart was each of their outbursts. The reason why they left then was because there was no point in a relationship where they don't even contact each other during the holidays.