Start with small cross rails with trot poles up to the small cross, make sure you go both ways evenly. From there when you are both ready go to a bit bigger... Have her go over small verticals and cross rails. Each horse takes to jumping differently and progress differently. Take your time, wear a helmet and if you can get a trainer out to help once in awhile. You know you can get alot of support and help with this here :) posting videos, keeping a training journal and always have someone out there with you when jumping. May sound dumb but last year met someone who was doing trot poles with her jumper in a lesson and her horse tripped she fell and broke her back in 5 places and had to take 2 years off and sell her horse! Be safe but have fun, take your time and lots of praise!
I have a 5 year old sport horse who was started over fences when I got him and mhe had about 4 months of under saddle work on him. He now has about 10 months and we are still working around the 2ft - 2'6 height area and we always go back and forth between trot poles. He is loving and and learning alot.