It is great that she is already good on the flat/dressage, because the better the flatwork the better the jumps.
Has she done any ground pole work, yet? If not this is where you will need to start. You can start with just one pole on the ground and walk over it a few times, if she is doing well with this and confident with it you can add more. You could set single poles down randomly around the arena and practice keeping a nice steady and relaxed walk going over all the poles. You could build up to placing 2 on each long side and 1 on each short side. After the walk feels good, you could try it in trot, keeping the relaxed rhythmic feeling that you had in walk. I would do all of this in a nice relaxed long and low frame.
Once that is going well you can try setting up about 3 poles in a row around 9 feet apart and walk over them, once that is going well you can try the same in trot. Once that is going well you could try around 4 poles but with the spacing set closer together, around 4 foot 6 inches apart or 5 foot (it kind of depends on how big your horse is or how big of a stride he has). Also remember to set the poles just to the inside of the track giving you enough room to be able to ride around the outside track. Also, never use only 2 poles set at the smaller distance, the horse may try and jump both at the same time, it is better to have at least 4 poles for this. Remember too, the smaller distance between the poles is for trotting only. You can both walk and trot over the poles set 9 feet apart though.
Once you can do all of this at the walk and trot keeping everything nice and relaxed and rhythmic, long and low, you could try setting down a single pole and canter over it. Then maybe set another one down on the other long side.
Just remember the goal is to be able to ride over the poles set out in a variety of different ways and in the walk trot and canter like they aren't even there. It should feel like your regular flatwork with poles in the way! Once you can do all this with your horse you can start to think about adding a low crosspole jump after a line of poles. Once you get to this stage I would suggest making sure to have someone experienced or preferably an instructor there with you who will help you to make sure everything is set up correctly and that you and your horse stay safe.