Judging from what little I know of his character (basically just the background and his recent thoughts), Chick would prefer it if the Matriarch died. However, it wouldn't be practical for Chick to kill her right now. He is literally surrounded by guards, and the mounted guards would be able to chase him down, if the raider elves didn't kill him first. Much safer instead to leave her to her own devices, maybe an elf will get lucky and do your work for you. This is undoubtedly the most dangerous option.
The second option: Run away. This would put Chick in more danger than he is right now, but not quite as much as openly attacking the Matriarch. As you would likely still be a target for the raiders, and would potentially turn yourself into a target for the guards who are still around and have their mounts ready to run you down once they figure out what you are doing. If you are going to do this, you will need supplies. The fallen have waterskins and weapons enough to support a short excursion into the wastes. Also that Amulet in the burning wagon sounds valuable, maybe you could make for a city and pawn it off. Risky, and riskier, but it is the option with the most reward.
The third option is to stay and fight. While there is a possibility for freedom that way, Chick might not fully believe it. On the other hand, the defiler is a clear and present danger, and it looks like they might be charging up for yet another Fireball or something worse, which poses a threat to Chick no matter what other course of action he may choose in the future. This is the prudent option, it has the highest chance for survival, and there may be an opportunity to pivot, should a better option present itself later in the battle. Chick seems to be highly apprehensive in his actions, so I would expect him to pick this one.