Before you haters go (if you're there), I want to do some more Lyra stories in the future, so I want to see some depiction of her roomate to help myself form some idea of what to make of Bon-Bon. All I could see myself doing is making her a support or an antagonist in the vaguest sense.
Some headcanon would be nice as well.
You can't just ignore Bon-Bon.

Bon-Bon is hot!

3772752 I've always imagined her to be somewhat emotionally disabled in some way due to a sort of mental disorder, like depression, or social anxiety. Lyra, however, compensates for both of them by being eccentric and otherwise unusual.

Not really a ground-breaking headcanon, but hopefully it helps in some way.

3772842 ...Ya'll is nasty.

3773155 I didn't ask you McMuffin!

3773180 And yet, here I am!
Back to haunt you from beyond the dollar menu...

3773759 I am more a Mcgriddle kinda guy and those hash browns!