I'm glad you took her headcollar off her. There has been one too many cases where equines have died as a result of owners leaving their headcollars on them. I no longer leave one on my own mare since she's previously caught her headcollar on fencing before and cut her face so I've definitely learned from my actions!
Horses that are hard to catch are unsure, disrespectful and fearful. Before training her my mare used to be the same, running away at any chance she got. Now she approaches me with enthusiasm and with a neigh.
You often get people recommending treats for a hard to catch horse but this is dangerous especially if you get crowded by other horses. Not only does it make the horse assume that you will always have treats, your horse is more likely to become pushier, nippy and impatient. If one day you arrive at that field without treats, that horse will have absolutely no reason to want to approach you, therefore the use of treats, in this case, is not beneficial.
Instead of trying to bribe your horse with treats I didn't fight my mare to try and get her to come in. Instead what I did was simply made the wrong thing hard and the right thing easy.
If I walked up to my mare and she turned to walk away, I'd simply tell her 'alright, you can go over there away from me but it's going to be hard work!' by moving her feet away from me but making her put some effort into her feet. If she's going to walk away I don't want her strolling, I want her sprinting putting all of her efforts into it! (Adding pressure).
Moving your horse's feet is your way of communicating that you are in charge.
Eventually, your horse/donkey will learn that actually, it's much easier to face you with respect. When your equine stops moving away from you and looks at you with both eyes and ears, reward them by walking away (releasing pressure). Give her some distance before approaching her again. It's useful to not look them directly in the eye as this is intimidating for a prey animal.
You'll find that eventually, she will figure out that running away is hard work and looking at you is easier. She'll grow more confident the more consistent you are with this and will walk towards you knowing that it is the easier option rather than losing weight by running away.
It's useful to practice this in an enclosed space once you've managed to catch her again. It does take patience but the long way round is always the right way with horses. There are no shortcuts in training equines.