Your mum is being protective, which is what mums do.
Have a talk to her, explain that you are growing up and part of growing up is showing that you can be trusted with some freedom, similar to what your friends already have.
You need to convince her that you will stay safe, only communicate with your friends, and show her you can be responsible.
Why not sugggest a trial period, say a month, and see if she can see that you are Ok with it?
Of course you will need to show that you are OK with it!!