Ok, so maybe Chie has already seen Boom, so she isn't excited or wowed by the introduction, probably puts on a bored attitude?
Maybe instead she spends the time looking at how her lance mates react to their cogs.  Maybe seeing them excited about their cogs/mechs will make them more relatable to Chie, or at the very least it's a common point for all 3 to get along?
She could also go over to one of the others and make snide comments on how their cogs are ok, but Boom is the best and most powerful, and give a whole specs list as proof.

Hope these help.