Well by her own frequent admittance, Jen has grown up her entire life overvalued:
“We demonstrate that narcissism in children is cultivated by parental overvaluation: parents believing their child to be more special and more entitled than others.”
https://www.pnas.org/doi/10.1073/pnas.1420870112
And then she found Brandon and a cult following of besties who also fawned over her like the sun shines out her bum.
Not sure what Tyler’s origin story is… sounds like the typical low self-esteem theatre kid who probably never felt like he got the adoration he deserved. So he used that as an excuse to treat women as disposable except for Shannon who is clearly his “main supply” of narc fuel.
Now Tyler knows he needs Jen to continue boosting his popularity but he really can’t stand her, which is why we see all the devaluation tactics (e.g., cutting her off, putting her down) now that most of the love bombing has subsided.
Jen can never be the “loser” especially not compared to Brandon and his goddess Tina so she’ll aggressively prop up the relationship for as long as possible despite zero effort on Tyler’s side to progress things to a deeper level. Notice there was zero mention of their “first anniversary” in February. If Tyler had made the slightest effort, Jen would’ve shouted that out to the moon.