How about this...

She wears the shit armor, rusty old armor from the basement baring no house insignias. She cleans the chamber pots. She does all the shit work and can't wear house colors until she earns it.

She essentially becomes the lowest-ranked member of the guard. Keeps her key.

I'm the sole no for one reason only... the story that could be told about her earning her place (or going further with it) is compelling. Kicking her out can be, too.

Nighttime peace and quiet was disrupted by a series of loud and sudden explosions that rocked the historic district. Witnesses claim the merchants and adventurers in the area banded together to fight back dozens of Duergar at the gate.

A few astute gossips claim that the Crimson Guard saved the city from certain peril.

Rumors of an attack at the dwarven embassy spread like wildfire. Citizens tell tales of a group of adventurers that fought back a horde of monsters from the Underdark itself.

Other citizens declare the Dwarves untrustworthy and claim they are somehow aligned with the duergar.