Well you have to pass through that cave to get to Violet from Cherrgrove, so it's not that bad? It definitely lives up to its name though, so bringing a Fire type would be good.

[He taps his chin. From what she's saying, he's guessing she's a newbie.]

That's where you're at, I'm guessing? Cherrygrove or New Bark Town? Either way, once you get a ride-able Pokemon it gets a lot easier.