Most player play a min-max-build. What level was the Javazone?
So she probably maxed her main attack with the Javeline to the cap for her level. Also, she might have done several special treasure runs, so she has a good equipement. Diablo 2 is all about that: The better the equipement, the better you come through the game. And if you min-max your character (e. g. using only one attack for 95% of the time and skill this attack to the cap, as well as the synergies to the cap as far as it is possible.) you’ll melt through the mobs like a hot knife through butter.
The game will get more difficult, however. The beginning in NM isn’t that difficult, yet. (compareable to the beginning of normal, realy.) But you will get a challenge pretty fast. Especially, if you play a character with only one damage-type. There will be immunes of all categories, even physical and magical. Act 1 begins with fire-immunes, so a fire-only-sorceress or a Fire-elemental-druid will have a much harder time to kill the mobs there, than an ice-specialized sorceress or Druid.
BTW: I think level 37 is pretty low for NM. I’m playing a Sorceress and I’m still in Act 5. (just reached level 40) And since the realy good stuff (beginning with the unique classe-items) starts at level 42, I think, I will not go there until I reached that level. (This isn’t so difficult, btw. You level realy fast at act 5, normal between level 30 and 40…)
There are also special regions to make treasure-runs. Pindleskin (a special unique-monster at the entrance of nihlataks temple.) is a realy good example for that. You can farm him about 10-12 times per hour (and this even isn’t pretty fast.) And he almost always drops a yellow item. Runes and Gems being just a bonus.
He and the mobs around him aren’t very difficult to defeat, get a relatively HUGE amount of exp and are Zombies, which resurrect on their own. Compared to arisens of a third monster, they even always give xp. (arisen monsters of a third source, like sarkrophagous in act 2 tombs, or the liches there, or the fallen in act 1 and so on, don’t give xp a second or third time.) So you not only get a huge amount of good items (especially, if you have treasure-found equipement on.) you also get a huge amount of exp. It’s common to get 3 level-ups per hour there… even in a solo-game. (without “players 8” command, because this isn’t available online…)
This are all reasons, why you can melt through mobs in act 1 NM. With ALL classes btw. You only need to be min-maxed and have good EQ.