@dlamay Great question! I am also a petite backpacker, but petite comes in many forms. It can refer to height, weight, shoulder/waist/frame size. If your petite refers to your height, as @REI-JenK said below, there are lots of options of packs that come in various torso lengths.
If your petite refers to your waist size, then when you try on these packs, make sure you can get the hipbelt snug around your waist/iliac crest with a little bit of room to make it tighter as needed. I have a petite waist (24") myself, so when I am trying on packs, that is always one of my first indicators as to whether the pack will work for me, even before I load it with weight.
Some packs, like the Gregory Deva even allow you to swap out the hipbelt for a smaller size. And Deuter tends to fit petite frames really well, even without the ability to swap out hipbelts.
Other tidbits I can also offer is that if your petite refers to your frame size, then you may also be bony. Moleskin is great for keeping blisters from forming, and I use it liberally on my hips and iliac crest where the hipbelt rests. I also have found that high-waisted leggings work the best for me, so that seams are not rubbing against my bony bits.
Pack as light as possible, but also bring plenty of layers for warmth. And lots of high-fat foods to help yourself stay warm. Trekking poles are also a really great idea for helping you balance and move with weight on your back.
Hope this helps!