>>64886038The two she's using have the most general use for beginner/mid-level players, most beginners stick with just 1 - a single style played well is more than enough to clear and get high ranks, the swapping experience she has from DMC3 was only added in the rerelease.
You can see high level players use all 4, but there's no reason to stay in gun or guard style for an extended period, so it's just popping in to use on of the fancy gun flex moves, or to parry a really big enemy attack for style points.
Really high level players do dumb shit like spam style swap between every blow in the combo just to flex by padding the game's APM to retardedly high levels.
