Crystal has a metric fuckload of ammo for all of her weapons, and several mutations that actually recover ammo alongside more mutations that make it more likely to regenerate ammo. So no, stamina battle won't happen. Gazef will be dead several times over before Crystal runs out of ammo for literally all of her weapons.
As for range? Crystal regularly fights at far ranges, because yea, a lot of creatures whip out some dangerous attacks at close range. Big Bandit can whip out a charge and kill Crystal in a single hit, Buff Alligator fires a massive shell of shotgun blasts at mid-short range (similar to Fourfold Slash of Light) that can kill or almost kill instantly, Assassin rushes at Crystal when she isn't looking with speed and does lots of damage, Crystal Spiders and Rats jump at Crystal and rush her down with higher speeds similar to Gazef, Snowbots charge at massive speeds similar to Gazef and do tremendous damage upon contact, Lil' Hunter likes to leap on Crystal and unload a load of danmaku in melee so quickly it's hard to realize what's happening before you're dead... A Fourfold Slash of Light is literally nothing special, and speed amps mean jack against strafing and teleportation, I've said.
Her defensive is offensive. Her defense involves a shower of danmaku, which incidentally slows Gazef's advance, unless your argument is that he'll charge directly into the attacks.
Gazef lost to a swarm of attacks raining upon him? Hrmm. Also, there is no good danmaku in Overlord, with the exception of possibly a few high-level spells used by Ainz or similar casters, which Gazef sure as **** has not faced. So a lot of his skill won't be important. Meanwhile, Crystal has faced enemies who one-shot or do sizable damage with singular shots so much, she pretty much expects it. That's how Nuclear Throne is, honestly. The entire game is just a bunch of enemies that either can chunk you pretty easily, or can wipe you out nigh-instantly. I know - I've been killed off by a stray Snowbot more times than I'd like to admit.
The skill argument is dubious, but it doesn't even address the main points. So far, Gazef really just... can't get close. And even then, Crystal is very skilled herself, and being a literal rock means that regular human physiology doesn't apply to her, thus even if Razor's Edge has full dura negation properties, it might miss a lethal blow, which would trigger Stress into a x2 amp. And with Crystal at x2 firing and swinging speeds, Gazef has absolutely no chance of getting past her.
All in all? Crystal's defensive maneuvers, teleportations on a pretty low cooldown (which is game mechanics, similar to Plant's snare), skill literally meant to directly combat people like Gazef including people faster than her.