Hello Kaplan,
When it comes to the USP I do something different that, immensely helps me clarify what my clients do... and what their position in the marketplace is.
I change the "Proposition" to "Position"
Unique Sales Position
Use this simple formula to get started:
* She helps [this group of people]...do [this benefit(s)]...[better,faster,easier etc.] than [her competitors or common fashion knowledge]
I don't know your client, so naturally I can't tell you what makes her different. Hopefully this simple formula will help you on your way to clarifying what it is she does and how it may be different.
Cheers!