If her entire purpose is to just be god-cop of Sigil -- and to be clear I don't disagree with that -- then have the good graces to make her boring! Don't put her on the cover and then have her the only detailed NPC. Don't make her face the logo! I don't know how you could possibly make her more front-and-center.The Lady of Pain is effectively the Goddess of Sigil (though yes I know she isn't a Deity), you aren't supposed to directly interact with Gods in most campaigns.
She's the sigil of Sigil!