Mika ends up watching the exchange without interrupting Serenity. She didn't exactly know all that much about back alley weapons deals, so she'd better let the seemingly more experienced Serenity take the lead. She does speak up once the immediate situation seems resolved, though: "... Okay then. I guess it can't hurt to take a look, right?" No, wait. It definitely could hurt, if something went wrong. But oh well. Might as well give it a try anyway, Mika wasn't going to get herself much of anywhere by avoiding potentially dangerous situations at this point.