She could invoke the oath. Tell Elathea to stop.
The cold pit in Gleam's gut says that's a very good way to end up with Elathea suffering the oath's backlash. Maybe it actually would stop her, it'd be better than having this fight here -
Gleam loves her wife, she remembers, in a soft, devastating moment. She takes a deep breath, feeling like she hasn't fully stopped, fully breathed since this began.