This was the second time that Erin had frozen up in the midst of battle and would have been defeated and killed already if it wasn't for Leon who saved her just in the nick of time each time.
Maybe it was because she couldn't use her other senses or because she had a fear of snakes, she didn't exactly know why but she did indeed freeze up, and she could hide from the fact that she blundered her life two times only to be saved by Leon.
She couldn't help but feel embarrassed as this was the same person she slapped and humiliated half an hour ago for being weak and looking for other options other than to fight.
Even though what she did in the heat of the moment was correct, there was no excuse for Leon to even suggest leaving their comrades behind while they ran with tails between their legs.