I think her mutation is midichlorians.

She is the Kaminoans first successful attempt at engineering a high midichlorian count into a deviant clone. I think they also swapped her gender too, from her accent I'd guess she's also a variation on the stock Jango Fett genetic sequence, they mention she's a clone, but never of who. I think it's safe to assume she is, though.

Her force powers haven't had a chance to mature to a noticeable point in her seemingly rigid and sterile upbringing on Kamino, maybe the rough upbringing she will experience with the Bad Batch may make her powers manifest over time.

Who knows, maybe we could even get an adult Omega - a force capable clone - in The Mandalorian. If another Imperial Remnant takes up Gideon's work into genetically engineering force sensitivity, studying Omega would be a good place to start.