Bitching is when a character who was previously an alpha (or sometimes a beta) becomes an omega, either because there are too many alphas in the area, or because they’ve been regularly submitting to another alpha (sexually or non-sexually), or they’ve ingested or been exposed to enough of another alpha’s pheromones or bodily fluids that their biology starts to change around it. There’s a lot of variation and the mechanism that triggers the bitching can really be anything you want.

[…]

We know Lucia and Livia are sisters. We know that Lucia was a Garlean spy when she first came to Ishgard. We know Gaius took them in (or at least, Livia in) when their parents were killed. Livia takes to their new foster father rather too quickly. Lucia has her doubts, and her relationship with her sister is becoming increasingly strained as a result.

Gaius wants to bring Lucia into the fold.

Livia has her own ideas about what that means.

Lucia wants her family back, but this isn’t her family.