Malinois

This will take time!  Especially as poor Amber had a pretty poor start in life and is less likely to trust people than most dogs.

Unfortunately, I suspect the spray collar and muzzle will have made the problem worse - as she will now associate both with being left with your Mum:  So being with Mum is now an unpleasant experience.  You need to make being with Mum a good experience, but it will take time with you and your Mum having a fun time together with Amber first.