So what exactly is the deal with Relena? Well you are about to learn about some early Western Otaku culture.

Relena is the lead female character of Gundam Wing acting as a lonely rich girl, self insert love interest of Heero, pacifist politician to a royal lineage she never knew she had and later Queen of the entire planet, even beyond the series she was holding high positions of power.
So what's her deal?
My opinion is that she kinda forces the plot to follow her script despite the fact that she is in Heero's words "In over her head" as her character has the most awkward transition up to her final role as politician.
The other issue is that the five Gundam pilots awakened the inner yaoi fangirl of the late 90s early 00s.
The boys of Gundam Wing were the anime equivalent of a boy band, the official art pushing that belief strongly with fans at the time, you had the bad boy, the fun boy, the quiet boy, the sensitive boy and the one who keeps leaving because of creative differences.
It's not really surprising considering scenes between Heero and Duo along with Trowa and Quatre could easily be interpreted as more than friends.
The Gundam boys were paired off with their own female characters but while most were at friend, sister or colleague levels of respect, Relena was the only one who was a threat to the yaoi fantasy, if Twitter existed back then, there would be a petition to get rid of Relena and make the Gundam boys canon gay, I wish I was joking, they live on through My Hero Academia instead.
But I find myself weirdly agreeing with them on at least Heero Yuy, because I think his character would've developed better without Relena.
My final thoughts on Relena is that she's a character that really didn't need to be that involved in the plot of Gundam Wing.