Big girls, you are beautiful...
Dressing to suit your shape - it's not always an easy task. However, a couple simple things to remember: wearing white on your largest part will only draw attention to that area, and having a sharp line cut across right above your largest part will also only draw further attention.
The combination of a dark waistcoat and leggings is leaving her with what appears to be a larger than life white tube around her hips.
This girl has got some style. I like the look she is going for (in fact, I am also after a waistcoat, and would probably wear it in a similar way).
She's not a lost cause... she's just not aware, or doesn't care, about what suits her shape. If she does, I'd advise she get a longer waistcoat that sits to her hip. If she doesn't, that's cool too. Not everyone is bothered about wearing things that compliment their shape. And, in the words of Mika...