I love Hello, I think it tops even MI, it's much more complicated, sadder and creepier in some way. But onto the interpretation:

The song has a lot of layers so it's kind of hard to see what there is in the bottom.

playground school bell rings again
rain clouds come to play again

I see this as an implication of her being teased at school, seriously, or at least if affecting her very seriously. The bell rings and the recess is over, she has to go back to class where she's all alone, rain clouds are dark thoughts and events that will come and haunt her. This could also be seen as an implication of growing up (I'll talk about this later), the recess is over, she can no longer be a child on a playground, she must enter adulthood which is so much darker, so much more difficult and she doesn't know if she can manage it. Maybe she's not even a child, she's just trapped in that world because being hurt all the time has stopped her growth, has forced her to build her own world where she can never be anything else than a little girl.

has no one told you she's not breathing?
hello i'm your mind giving you someone to talk to
hello

This is tricky. It seems partially that a part of her that still believes somebody could help her tries to ask the world, the people around her if they can't really see that she's lost her soul, her life, her breath, she's afraid she can never be whole again, she's lost her self-esteem, and feels she's slipping away. I think she's also trying to be drastic here, not breathing equals dying, and she's a nice girl who'd never talk about suicide, who'd never do anything so "bad" or "selfish" but now she feels like maybe it'll be her only choice and she's somehow trying to bring the thought out but can't say it as herself, she says it like it was about somebody outside of her. She seems to create another person entirely, her mind, as it were, to help her and be there for her, somebody who seems older, wiser than she is. So in a way I think the lyrics above could be also understood as this separate mind-person telling the girl, can't you see you're killing yourself, you're burying your own mind, you have to be stronger.

if i smile and don't believe
soon i know i'll wake from this dream

It's useless for her to believe she could ever be happy or be left alone by the people causing her pain and if she would let herself be in peace, soon something would happen to make her feel even worse, something would snap her back to the horrible reality.

don't try to fix me i'm not broken

This is a thought that I can relate to as a kind of a depressed person. You know (or just think, but in you're head it's the absolute reality) you're not alright, you know you won't fit in, ever. Nobody will ever see you, really. But still, you don't want to change yourself. Your own soul is all you've got and even if it is a little twisted already, it's still yours. The world is the one that's wrong, not you and it just makes you feel worse that nobody sees it, nobody tries to help you. Just because you're withdrawn and strange, it doesn't mean something's wrong with you. If you try to ask for help, people say "you should just get it together, try harder, stop being such a cry-baby" and it makes you feel like you want to die.

hello i'm the lie living for you so you can hide
don't cry

This is the mind-person again, she turns up every time the girl has a more difficult thought in her head, a one she can't believe she's thinking, something that's truly what's in her heart but not okay. I think she's a very good girl and the darkness inside of her, caused by the pain people have made her suffer, scares her and is alien to her, she tries to channel it to another person. In this part, though, it seems that she puts on a shell, she hides behind the person or personality she created. She won't show her pain to anybody, she'll hide away her real self, even if won't do any good, but she has to do it, to preserve something real in herself.

suddenly i know i'm not sleeping
hello i'm still here
all that's left of yesterday

This is where something drastic happens. I don't quite know what. Sometimes I think that there's a theme of growing up in here and at the end she realizes that she's trapped, she never had any support, she was just an object of ridicule and she felt nothing but pain, she can't move on, she can't evolve, she can never be an adult. She's in a coffin. Then other times I think the mind-person she created took her over. She can no longer control it. She lost herself and she wakes up into the knowledge of being controlled by something else, something inside her own head.

Then I also see a more positive ending in these last lines. In it she wakes up, all the lines are spoken by her now, the "Hello I'm still here" is hers now and not the mind-persons like it was everytime earlier in the song. She stands up and even if she's shattered and hurting, she now demands the attention and not just tries to ask for it quietly. The end isn't horrible positive, maybe it was the wrong word. She's still messed up and sees the problem of not being able to move forward (All that's left of yesterday, which could also mean for the people hurting her that she's a reminder of the things they did wrong, they must take responsibility) and doesn't know what to do, doesn't know how to live, but is still angry and finds her own voice and isn't a victim anymore. Also, she has to break her own shell, her coffin and be strong, not to hide in her own head, that's the only way for her to grown into her own person.

Well, this is like a forever-long post, sorry I'm a bit weird sometimes. But I just love analyzing things sooo much