The problem with the whole idea of Ash and Serena getting into an argument is that for the most part it would feel forced. Although if they did get into an argument it would probably be due to a misunderstanding. Althoguh I don't think the shipping really needs them to get into argument.
She's been angry at Ash before, remember the pokevision episode? he accidentally ruined her hair and outfit and she flipped her sh*t so maybe something like that to happen like the outfit her mum got her but it was a complete accident and Ash tries his best to repair it by getting a new one or taking it somewhere to be fixed, something like that. But like i said it's just to make things seem more interesting