"Yes, because I regularly turn things into pits of boiling rock on you."

... Yes, she was definitely feeling fatigued with the whole GLaDOS situation. Which was fine and dandy until he was rearing up, which felt like a stupidly dangerous situation. She ended up yanking on the reins accidentally before hugging his neck, clinging to him and shouting, "Marco, calm down!" and sounding more exasperated than concerned.

She half figured he was having her for a lark, except for the fact that he wasn't usually this piss poor in choosing the timing of his jests. Or jests like this at all. Marco liked using words.

Probably because those could be tossed out on the run. Not everyone could string sentences together most the time.

Then the gate closed behind him, and something blared. The gate in front of Marco swung open, and they were both faced with open track.

Open track, and fourteen other lunging horses all at once.

"Okay, go!" And please, please, please don't do anything that will get her thrown off. The chakra she'd waste making sure her fall wasn't injurous would be more than she quite had back yet.

Damn GLaDOS for not having provisions for soldier pills!