Well, first make sure she’s comfortable with a harness on. Most bunnies can’t compete in those videos you see of bunny hopping competitions. The rabbit has to be totally alright in the harness; it’s just unnecessary stress if you try to make the bun be comfortable in it.
Then, always avoid collars. Always use a harness. And I would personally avoid dog harnesses just because they’re too heavy for a bun that’s not a Flemish giant. I’d also get a harness from a store so that you could return it easily if your bun turns out to hate it, which is likely.
Just a heads up; always train indoors where it wouldn’t be a big deal if you had to let go of the leash. If your bun is totally comfortable in the harness, then your biggest threat is them taking off while you’re still holding the leash. This is totally likely, and could cause serious injury. Bunnies are fragile. If your bun starts running, let go of the leash.
Good luck! Just remember to take it super slow with the training and always make sure the bunny likes it as much as you do.