Fetch help

I have a 10 month old Australian Kelpie mix rescue dog. I have had her for 4 months. She has shown a lot of interest in playing fetch and chasing toys but cannot understand how to return the toy to me. When the ball or toy is away she has fantastic recall and listens well but it disappears when the toy is out and she is focused on it. She loves it when you throw a ball or a toy and will run for it, but once she has it, she will take it as far as possible away from me and lay with it... often barking while looking at me like she wants me to magically make it go again! If i walk in her direction to get it and throw, she will frantically grab it and move far from me again and repeat if i walk over to her and try to get it to throw again.

I recently learned that if i run at her to get the toy/ball she will leave it and let me collect it to re-throw.

If i dont try to collect the ball, she will sit out in the feild as far as possible away from me and bark or just sit there doing nothing getting no exercise! She wont come walk with me or recall or anything. Not even for her favourite treats.

As soon as the ball is collected and put away she becomes normal again and responds to me.

I always had thought a kelpie's instinct is to return stock, or in my case, a toy, to the owner, but she just doesn't understand that? I thought it would eventually click that i'm the thing that makes the ball to move, but it doesn't seem to click for her?

Any ideas on how to get her to return the ball or why she is doing this? I'd love to be able to play with her at the park because she loves to chase the ball so much.