My mum found my private tumblr and wants to "talk"?

[Niamh]

I accidentally left my tumblr open on Thursday night when I locked the family iPad, and my mum opened it a few hours later and looked at it. My tumblr is private and has a lot of stuff about my depression, my self harming and suicidal thoughts, it also has a lot about my feelings. She mentioned it briefly yesterday morning, expressing concern, but after a quick discussion and me saying I was okay now and that all those posts are old, we left it. Now today, I accidentally opened her facebook message when I tried to get rid of the notification and the message she sent to a friend said that she's taking me to the doctor's on Monday and taking me out tomorrow alone to talk about it all, she also said Im unaware that she looked at ALL my posts, all of which she hasn't told me about. Now I'm absolutely petrified, I don't know what she's going to say or what I'm going to say, we're not exactly close. I didn't want her to know about my feelings as she may feel let down, and she might be so patronising for the rest of my life now. I'm really scared, any advice about what to do?