In canon, Une is rather diminutive since she stands at 161 centimeters (5 feet and 3 inches) and weighs 47 kilograms (103 pounds).This is probably a consequence of her tough military training and part of being a Mobile Suit pilot. You have to fit into those skin tight spacesuits. She was also comatose for a few months and probably survived mostly through feeding tubes so that's a factor in her skinny frame. I doubt she takes her time to sit down and eat unless she absolutely needs to so there's another reason why she can somewhat be considered a whisp of a girl. I like to thing she has a bit more meat on her bones as Elle. Less stress to contend with.

Her long brown hair is worn loose when she serves as OZ's representative to the colonies in the series as well as when she leads the World Nation forces at the end of the First Eve War onwards. This is the hairstyle she wears as Elle. She's also been known to wear her hair in two braids rolled into buns and tied with pink ribbon when in her crimson OZ uniform earlier in the series. She looks like she has cinnamon rolls on her head. With that severe hairstyle, she would keep her brown eyes behind round eyeglasses. She doesn't wear glasses in game but I like to think she keeps a pair of reading glasses around.

Her usual attire from this canon point consists of smart skirt suits (we see her in one pink and one purple ensemble) and her Preventer uniform consisting of: a green uniform jacket with the Preventer logo emblazoned on the shoulders, a dress shirt in a lighter green worn under it, a dark green tie and a short skirt matching her jacket in shade along with a pair of smart heels. When out in action, the heels are traded in for combat boots and she wears tights under the skirt. Here's a picture.  Her wardrobe as Elle is pretty similar. She dresses like a businesswoman. Skirt suits and heels all the way. There's hardly ever a time when she dresses sloppy. When she does, it usually means something's wrong.

In terms of identifying marks, she has a bullet scar from being shot by Tuberov in the chest and it looks a bit like this. Right in the middle.

In terms of celebrity resemblance, I use Troian Bellisario as a PB because I'm ridiculous because I like being able to picture her in clothes that aren't military uniforms or from 1995 sometimes. Also dumb kissing icons. If I ever use usually or prevents with you, that's what's up. Of course I'll ask if it's ok first. :> I just really adore how Troian's wardrobe on Pretty Little Liars pretty much matches Une's to some degree too. OTL And she's supposed to be attractive since men who are not Treize or Zechs or Gundam pilots follow her around like puppies in canon plus she has a good camera presence for press cons and speeches so w e l p.

Mind you, she doesn't think she's all that attractive? She knows she's pretty but she's not exactly a beauty. She thinks she's pretty plain and that it's mostly confidence that carries her. A peahen is brown and plain but all the peacocks flock to impress her because she knows how to carry herself. In canon, she also has a heavy fixation on mirrors and there are a bunch of scenes where she's dressed and undressed to transition between being a harsh colonel to being a diplomat. I mean one of her major weapons is EXPLODING COMPACT POWDER. Make-up and a mirror in there. She knows appearances are a big deal and her change in looks is a big part of her character development.

Oh, and she wears a lemon vanilla perfume. Blending sweetness and tartness. Sometimes she wears a rose fragrance as well.