I think its normal baby behavior, she's only 4 months old you said right? It's common for young foals to be nervous, and you said she was just a weanling correct? If this is all true, it could just be that she is having separation issues or had a bad experience, maybe with an ungentle handler. Don't take it personal, it doesn't sound like it's anything you are doing wrong. I would suggest though using the feed bucket as a reward. The way you could do this would be to offer her the feed bucket but when she comes towards you give her a small taste the first time and then attempt to stroke her, if she pulls away, pull away the bucket. Don't ever make fast movements because they only cause confusion. Do everything nice and slow and take your time, it will require patience but you should be able to stroke her neck when she eats after a feeding or two. Gradually increase the areas that she will allow you to stroke her after she is comfortable with one area you have been stroking often. Just take things very slow and don't loose your patience. Weanlings are like toddlers, they can get easily confused, distracted, or scared, and will remember the events.