I'm going to go out on a limb and say Vanessa is a fair bit smarter than Ozruk. He's a giant rock and shes the mastermind of a criminal organization with a vast knowledge of poisons. Vanessa is also quite small compared to Ozruk which does mean he can squash her like a bug but it also means she's going to be hard to hit.

Now the Elementium Spike Shield does pose a problem for Vanessa but there's no reason to think after one hit she'll learn to avoid that (it doesn't exactly last the whole fight.) But this leaves her open to the deadly Paralyze Shatter combination. Or so you would think. If Backslash is anything like Cloak of Shadows then Paralyze isn't going to do a thing and she simply avoids the Shatter.

Vanessa would probably win as long as she doesn't make a mistake.

You're not taking into account cooldowns on abilities. If the abilities have cooldowns like in the game, Ozzie should use the abilities more often than Vanessa can Backlash.
If not, he's just have to Shatter constantly and Vanessa wouldnt be able to get near him. I'd rather think of the fight having cooldowns.

And Ozzie never had any problem hitting gnomes so a female human is big enough to hit.

Also, I really dont think that a 16 year old is smarter than an elemental being that has existed since Deepholm was created. He never showed any sign of lack of inteligence. His vocabulary is not like Hulk's and he chose a small tunnel to make his stand instead of the big areas of the rest of the cave. To me that shows some inteligence.