There are probably paths that the orcs prefer traveling in the forest, so she probably would have figured out where to set traps.
Like I said, she couldn't have placed them near the orc camp because the regular patrols would have noticed the traps, like after stepping into them. The traps would have needed to remain hidden until the orc troops started marching toward the human town. However, it's not like the orcs kept continuously sending groups of brutes to check out the human town, so Aria wouldn't know where to set the traps.
But, traps require a lot of time in a forest.
I said what I said because she should have had some spare time, from hunting and poisoning. She would also be under consistent stress since she couldn't possibly know when the orcs were planning to launch their assault. She made a good guess with offering the animal carcasses, imagining it might satisfy the orcs for a while, postponing the attack. No guarantees, though. The orc general might have just suddenly one day felt like attacking and that would be it. So, building traps could have allowed her to cope with the pressure.
You have to dig holes, or cut trees for spikes. So first I would say that she didn't have the manpower for such a plan, because she's not preparing traps for a few opponents but for an entire village of orcs.
Every orc down count. Furthermore, if she could have prepared a field of traps, even if they were rather flimsy traps, concentrated in a suitable place, she could have used the chaos to launch sneak attacks, when the orcs' attention was elsewhere.
I'd say that traps make more sense near the human village in a siege situation. There's some distance between the village taken over by the orcs and the human village, so once she was locked in to the plan of observing and poisoning them, to ensure she can react whenever they decide to attack the human village, there was no leeway to go back. Traps would have been the responsibility of the soldiers back at the village and they were busy just evacuating.
Let's hope Kevin and his merry bunch had the wits to think that far ahead and prepare traps. I wouldn't count on it.