All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.
You have to know, dear sister, that Allaah has made this life a test. Allaah says (interpretation of meaning): {…and We shall make a trial of you with evil and with good, and to Us you will be returned.}[21:35]. So a Muslim has to be patient about the difficulties and hardship that he/she faces. The Prophet said: "The believing male and the believing female continue to be afflicted in their own self, children and wealth until one of them meets his/her Lord without a sin." [At-Tirmithi] So we advise you to be patient.
As regards writing a diary about daily incidents, there is no harm in this if it does not contain any prohibition. If you have written something bad about your mother's family, then you are wrong and should repent and ask their forgiveness. Anyway, we advise you to keep good relationships with them at all times. Imaam Muslim reported that a man came to the Prophet and said: 'O Allaah’s messenger! My relatives are such that I maintain ties with them, but they abandon me; I am kind to them but they ill-treat me; I forbear and they are rude to me'. The beloved Prophet said: "If you are as you say, it is as if you are feeding them with hot ash; and so long as you continue as you are, Allaah will help you and He will protect you against their mischief."
There is no doubt that your girl friend misbehaved by spreading your secrets as she informed your mother's family of that which spoiled your relationship them. This is considered as slandering. Concerning your informing her about the treatment of your mother's family towards you, if it was not for a valid purpose, like being wronged and the like, then it is backbiting. You should not cut relationship with this friend of yours, but rather you should advise her about what she did.
A Muslim should conceal what is related to his/her private life. If he/she has to reveal some of it, then this has to be revealed to someone trustworthy provided that this does not lead to transgressing other people's rights.
Finally, we advise you to be dutiful and kind to your parents at all times. If you cannot visit your mother, then you can be kind to her by telephoning her, or sending her a gift, or supplicating for her and the like.
Allaah knows best.