I don't think there is anything Yasha can do... Her shots, even coming from a rifle (with a target finding spell) can't hit Sena, it doesn't matter if she conceals her presence before taking the shot. Even her strongest attack can't seem to be able to pass through her barrier, or do any type of damage at all... Her strongest attack wasn't even able to cripple Senna, not even a but.
Not even Selena's curses are effective against her.

Yasha is powerful? Yes. She is meant to be a glass cannon. That means that if Semana threw her sword at Yasha or if somehow she got nearby her, Yasha would [I]die[/I]. Since Yasha has no armor or any defense at all. Literally no defense at all.