K., first, I truly feel for your daughter. But it sounds like the one with the issue here isn't her, it's you. Reread your posting: "She's OK with it," "I feel bad," "I (not she) do not want her to wear the Goodnights for two more years" etc.
Please be aware that if you send out the vibe that there's something wrong with her using the Goodnights, she will pick up on that and it will upset her. She is being very mature for nine years old if she understands, which she seems to, that this is a purely physical medical issue over which she has no control, and that she needs to wear the Goodnights. Well, some adults --and not just older ones -- need help with bladder issues too! She at least will outgrow hers, and in what will be in reality a very short time.
Why medicate her just for something that is taken care of with the Goodnights? Why risk side effects etc.? If this isn't a lifelong thing, let her body work it out by itself. If she is fine during the day and the only problem is nighttimes, she's doing great; please praise her and reinforce how grown-up she is to understand what's happening with her body. If you use terms like "diaper" in her hearing, think how she will feel about herself.
Please think about why you feel so worried about it. Are family members or adult friends of yours pressuring you -- or hassling her -- to get her "out of diapers"? If so, that's their problem if they see it that way. Be confident that she's OK and you did the right things: You did exactly the correct thing to get her to good doctors; you have the diagnosis; you know it will right itself pretty soon; support her and don't even mention this, just put on the Goodnights and tell anyone who may be pressuring you that this is between you and her and to change the topic. If she is otherwise healthy and happy you are both doing well.