I usually wear the model size. I'm 115lbs, and 5'4. I ordered an XS. It does run big in the shoulders. I'll have to see about whether I want to alter it. But it's nice, color and quality are great. It feels nice. I like that it's a bit of a feminine take on someone wearing their partner's dinner jacket.
Rated 2 on a scale of minus 2 to 2, where minus 2 is Runs Small, 0 is True to Size and 2 is Runs Large