...How do you get a bird used to a towel? I've watched them do it on video's but their birds are already used to it.
You work within her comfort level and get her used to it by degrees. Keep her on a training perch or some such and approach her with towel in hand. Make sure to keep the towel below her level. Approach until you see the first subtle hints of unease (a fidget, a nervous glance), then stop. No closer. Don't risk panicked flight. Wait there a few moments and then, if you are within arms reach, reward with one of her favored treats and retreat. (Just reaching with your arm. Keep that towel away.) If you're farther than arms reach, just retreat.
A few minutes later, try again. Try to get a little closer. If you manage it, reward her again. Either with a treat or, if still too far, with the retreat of the towel.
The goal is to get incrementally closer. Gradually. So that she begins to get used to it. And keep the sessions relatively short. Maybe 20 minutes, depending on her attention span. And if she begins to tire or show stress, don't be afraid to call it a day. There's no rush. In fact, rushing the process will only delay your ultimate success.
Eventually you'll be almost close enough to touch. Even then... especially then... you don't want to rush. Reward her for enduring the towel's proximity. Carry this technique through until you can actually touch her with the towel. Treat liberally.
Following the logical progression, you'll eventually be able to get the towel around her. It might take time, but the result will be well worth it.
Of course, you can't really start working on this until after she's finished her current course of meds.
Hope this all helps.