I also get angry and say nasty things to the people I love. I honestly do not mean them, they do not come from any seed of truth in my heart. They come from jealousy and anger percolated through the negativity of depression. I hope you can find some peace... I am sure the insecurity you feel is a result of depression... And with some healing the possibility of returning to a good relationship with your friend. I think (just my opinion) that this will require some healing for yourself and some understanding of what you are going through on her part. You are in charge of the former but the latter will be up to her. Maybe some other trusted friends can help you.