A possible explanation is that for all her arrogance and bravado, she actually realizes she's incapable of reaching her people on her own. She's already been captured twice, by beings certainly much below her (in her mind) the second time, and thus sees the part as a necessary evil for the time being. Not that she'd ever admit this. It would make sense for her to abandon the party
once we reach the githyanki patrol
but it very quickly becomes apparent that's not viable.
Since we've not been able to reach her objective during early access, it's hard to say what justification there is after that. But if suspension of disbelief isn't possible even knowing the clear gameplay reason she sticks around then you'll just have to replace her with a custom fighter ASAP. Harsh I guess, but that's the card that's been dealt.
