Bluemoon is obviously from a completely different Pack. Once she starts gaining her Thunder marks, she starts forgetting her place in Spark Pack, and Spark Pack as a whole, until during a battle she suddenly uses her Spark power and gains a Spark mark. All her life, she'd never been able to use that power, but now that she's in Thunder Pack and she's able to use The Power of The Storm, she doesn't need to use her birth magic. Now, with two marks from different Packs, she finally has to choose whose side she's on.