IMO it doesn't matter if she went to Northwestern. She knows that's an iconic Di picture. She knows she's been accused in the past of cosplaying her MIL.
Why would you even put that jumper on? There's a million other jumpers on the planet. And that clip of her just gurning at the camera in said jumper between the flower clips. It's all just so odd?
Did Harry film it and she thought - "oh that's mint that I'll post it"
She blows my brain I honestly cannot fathom her thought processes at all