The most important thing about greens is to be sure to be introducing very slowly and only one type at a time.
For example, say you want to introduce kale. Day 1, you offer a small (maybe thumb-sized) piece. If she eats it, great. Offer the same the next day and the next, increasing the amount each day for several days. Keep an eye on her poos. Any changes? Stop that green. If all is well, then great. That's 'acceptable green #1'.
Green #2 can be tried a couple days after you've finished the week of kale. Go through the same process. Only one green at a time. The reason for this is so that you can determine if a particular green causes tummy issues. If she had gotten a whole variety at one time, then you wouldn't know which one was the problem.
If she ever doesn't seem keen on something, don't give up. Try offering it several times over several days. Sometimes they reject the unfamiliar.
Once you have her used to a variety of greens, she can have them daily. The goal should be 2-4 cups per day (per House Rabbit Society). Certain greens may be too high in calcium or oxolates for daily feeding. In those cases, just rotate different greens in their place for a few days.
For a starter list of what to try (and which ones to limit) check here:
https://rabbitsindoors.weebly.com/greens--veggies.html