If and when you are ready to return, you will feel stronger, and able to face her secure in the knowledge that you are the better person. It will take time for you to acknowledge this, because at the moment you probably feel worthless and as if you are to blame for being weak - this is normal for people with depression. Counselling and/or CBT would help you to feel better about yourself - ask your GP to put your name down now, as there is usually a waiting list. Alternatively, most schools have sickness protection insurance, and there is often a counselling/CBT service offered to staff in conjunction with this - if you don't feel able to ring the school yourself to ask about it, see if your friend or a sympathetic staff member would ask for you. There is always light at the end of the tunnel - right now you can't see it, but that doesn't mean it isn't there.