I’m with @Katt and @Francisco about the Return to Sender Spell- this is a good way to both protect yourself and send a “don’t mess with me” message to this ‘friend’.
If the idea of retribution magick doesn’t sit well with you, I also suggest surrounding yourself with protective objects. You may want to take a look at this discussion on making Protection Bottles, and @SilverBear shared a beautiful and easy Protection Meditation 
Here are some Crystals for Protection 
, and for herbs both Cloves and Aloe Vera have protective properties.
Best of luck to you, @nina and stay safe! 