A teacher's diary

How can I go on this way? I just had a delicate and frustrating situation today; one student of mine, in the end of the class, told me she didn't understand nothing I was talking about. The subject was the Present Perfect. And all the last classes I had given them a lot of exercises about it, and I tried again to explain for her, but without succes. Then, I just told her to get the answers of the exercise from one of her colleagues, and suddenly she said: but how do I get the answers if I do not understand nothing... and I had no answer. It was frsutating for me, but, at the same time, my will was telling her: "you're such a fool, you'll never understand nothing, it doesn't matter how long you study". Of course I didn't tell her that, but that is really my opinion. She is the kind of person that may study a long time, but will never learn, even if she start from the starter level. She is  a fool!! I think she has some kind of dislexis or delay in her mind... and it get me thinking, what can I do? how teachers deal with that? I think our tendency is to give up, to ignore this kind of student, but we cannot do that! as an educator, I cannot do that! So, I know what do not do, but I don't know what to do!! I feel I'm in chains, in a labirint: what should I do, or what I must do?
I feel like telling her to give up or to treat her mind... she has to have a disturb, it is not possible... and I must do something, investigate, study, learn, I don't know, just must act somehow, someway.

I feel like crying... I need a B plan because my A plan may be failed... I'm getting lost in this world, God save me, bye.