The thing is.
Yes affairs do happen
Yes people do leave their partners and marry the afairee (?? !!)
BUT
Where she made everything one hundred times worse was
Having a huge wedding
Selling the photos to a magazine
Writing a book in detail about the affair and the first time their lips touched bollox.
And generally rubbing Della and the childrens nose in it.
A quiet wedding with a couple of witnesses and slink out of the limelight to live happily (or not in this case) ever after.
She played it wrong. She stole another woman's husband, and expect the world to be nothing other than delighted with the fact. How stupid could she be. And he is an arseholio of course too.
And I agree whole heartedly about the dusty box in the attic. Maybe she can make a few bob suing the DM for starters. She must be 'Disgusted of Esher' or wherever she lives.