I don't think this girl is naturally jealous. I think her ex manipulated and abused her into feeling very insecure and likely activated her attachment trauma. Because someone saying "go find yourself for a year while I wait" is NOT a jealous person. They do likely have a pretty low self esteem though, especially to put up with all the other toxicity.
I think that her ex hides her age to do this exact thing. She seems like a master manipulator and prefers to prey on younger women to get away with it. Maybe she’s done this before.
In my 20s I dated several guys (in a row) who were in popular local bands. I, too, thought I had "jealousy issues" -- but coincidentally, each one cheated on me. It's not "jealousy issues" - it's having fantastic intuition.
I hate cheaters so much. Cheating on someone who you sleep next to or who your supposed to love. I get falling out of love but just break up instead of betraying them. Or if you know you have feelings for someone else talk it out with partner or someone or just break up before it gets into cheating territory.
This right here is why people like that date people in their early twenties, because in your thirties you recognize a liar the second you find out they put the wrong age on their profile.
Sucks that we often have to learn these things the hard way, I hope she can deal with her codependency issues after this, I suspect she doesn’t have jealousy issues at all and that was just gaslighting from her wife