A deal is a deal,

which could only happen after both (or multiple) sides agreed. Fair or not, becomes irrelevant.
I was commenting, after 晓风残月 asked 有什么好办法可以化解吗？Not about right or wrong.
Bear this in mind, given where they are at, the difference narrowed down to B-15W vs A-22W (that 7W difference is not even real money, just loan amount).
Other stories and 寒心 are irrelevant. When you have a dispute and want mitigation: a) focus on this, or b) bring in everything, but no selective piece-meal in the middle.
If they want to break now (not easy) or in the future, another topic.