The thing about him now being more valuable because he has a hot ex is pretty disgusting to be honest. Now, to be fair, in early days when you know that someone with hot exes is attracted to you, that can be flattering and make you feel more interested in him. But conversely if the exes are less hot than you, then there's little sense of inferiority.
But Liz is supposed to be marrying this fellow and they've been together a couple of years now. It's ridiculous and demeaning to David. He's just an object to her, like a pair of shoes or a borrowed designer outfit.
And then after the faux outrage at discovering he was already involved with his wife to be when she was moping deludedly after him and not getting the message, there's the expected self hate.
FFS Liz you never had a relationship with him then. He was an acquaintance you had a crush on, an unreciprocated crush.
You have a relationship with him, a real one, NOW. It began when you started going out together a couple of years ago. It did not begin in the 80s, FFS.
I had two relationships - real ones, with sex and "my boyfriend" and everything - with the same man, several years apart. The two relationships were quite different due to our different stages of life and the ONLY thing that was different second time round was that we already knew each other's likes and dislikes, weird habits and suchlike.
Liz isn't even in that situation.