So if you know that so far she likes lettuce and corn give it to her every day. The lettuce should be either romaine or green leaf-(regular iceberg lettuce has no nutritional value).
The bigger variety every day the better I think, because dif vegs have dif nutrients.
Did she try the celery? And you might want to try some fresh broccoli-I think it's one of the favorites.
Whatever she likes just keep giving it to her and try to add new ones.Even if she doesn't like something the first couple times you give it to her, just keep trying.
Oh, and grated carrots is usually a good one too