Friendly!Girl: [says perfectly reasonable thing]
Friendly!Girl: [doesn't immediatly drop everything to attend to Anna's angst]
Friendly!Girl: [disagrees with something Anna said]
Grumpy!Anna: Bite me!
Friendly!Girl: [displays 'evidence' of liking someone else better, perhaps by agreeing with their opinion instead of Anna's]
Grumpy!Anna: Wail! I am unloved! [existential crisis, fannish crisis, desire for cookies] Everything sucks! If only Mulder were here! He would understand my pain! Sniff.
Grumpiness can also be triggered by blase gym attendants who answer the question "Do you have a rowing machine?" with "No." Bastards.