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No he tricked her into ejecting. This was set up several panels back, when she made it obvious she was not going to let him take on the Slaneshii avatar alone. That makes the act his noble self sacrifice, not her screwing him over.
The setup is what I mean too. She insisted on accompanying him (for no good reason that I can see) and he gave in so now she's got his ejector seat b/c he didn't have time to argue with her and / or the strength to just push her out of the mech.