Salam Dear Sister,
Thank you so much for this question and for contacting Ask About Islam.
It is very thoughtful of you to explain these issues adequately to your Mom. May Allah help you articulate matters clearly, and may He help her see the wisdom, beauty and peace that is in all the teachings of Islam!
With regards to your question, AboutIslam.net has a lot of resources on the subject and has in fact covered this topic quite extensively.
So, we will recommend here a few resources for you to read and explain to your Mom, hoping this will make matters easy for both of you.
To start with, here are some diverse articles and answers that have been covered on the subject:
Additionally, you can find here all articles on hijab on AboutIslam.net.
With regards to the videos, below are some interesting ones by various speakers and from different backgrounds so that your Mom can see the topic from diverse perspectives. Hope this benefits and sends a strong and positive message to her, insha’Allah (God willing).
Please don’t hesitate to ask us for more resources or any help, and we hope you read/watch and benefit from the above.