I'm almost 5'4", weigh 115 lbs, and wear an XS. Keep in mind that this is a race fit and it's supposed to be skin tight. It fits me perfectly in the chest (32" chest), arm cuffs, and belly area.
The photo shows a solid purple jersey, but the actual jersey is very thin and somewhat see through so it does not look like the photo exactly. I could see my bib underneath... Still a nice jersey though. The material is very soft and is not a waffle pattern so hopefully the UPF 50 rating is correct.