I could relate in a way.
5/5

Her life is nothing but darkness
and she can't find the light
she cuts herself till the sink runs red
and cries herself to bed

^It's a good opener for the piece, but in the last time, I think you should change "bed" to "sleep" It would help make the stanza flow better, in my opinion.

when will she see that i am here
have always been here for far to long
wish she would open her eyes
why can't she see that together we belong

^In the second line, the "to" should be "too" . The second and third line, I think, you should reword to make it flow nicer. .Like, "And I've been here, for far too long. I wish she'd just open her eyes" . These aren't big changes, just minor details that could be adjusted, you know. But I like the last line. It was a bit cliche, but nicely done. :]

i don't want to be just a friend
i want to mend her broken heart
no pain would ever inflict her again
because we would never be apart

^In the first line, I think you should take out the "a" and change "friend" to "friends" . I think that the line would flow more that way. . and the rest of the stanza was very nicely written. :]

Together we could be one in every way
Does she know that I think about her all day?
Why can't she see that I'm right here and always will
I guess I'll keep waiting until....

^ In the second line, you should change "all" to "every" . Again, the flow. . And for the last line, you should add the word "on" between "keep" and "waiting" . But this, I think, was a good closer for the poem. :]

So these are just a few suggestions. You don't have to listen to me, but this is just what I think you should adjust in your poem. Because, this is piece IS good, but it can be better. :]
Anyway, I really like the first and third stanza, a lot of emotions drawn into those few lines and portrayed very nicely. :]

Oh and also. .I think that with your rhyme scheme, it was a bit forced. And that made your poem kind of. .off, you know. I think you should try free verse. It might help. :]