Your book sounds like it was really great, the concept sounds very fun and unique. Do your work justice and get the treatment so you can rewrite and finish it. Just think: this new version will be even better than the last, because now not only do you have more practice writing, but also every time a story is edited, it gets better. You can use this as an opportunity to improve the story: maybe they're a more interesting way to begin the work, or maybe a character would be more compelling if they were slightly altered. Maybe you'll think of an entirely better idea for a novel, and work on that one.

You can also use this as an opportunity to gain some leverage over your mother. My mom also really discourages my solitary passions (I'm an introverted writer too!) and tries to force me to be "normal." She also took my computer away and has thrown out my work before, so I can kind of understand what you're going through. Tell your mom that you will only undergo treatment is she promises never to destroy your work or take away the computer again, because it's your life's passion and what makes your life worth living, and without it you don't want to get better. If you explain this to her calmly and seriously, I think (hope) she will understand how important this is to you, and promise, and hopefully keep her word.

In the meantime, to help you cope with the loss of your work, I recommend reading Misery by Steven King. It's a really beautiful novel, and in a lot of ways it's about an author who has to cope with the destruction of his magnum opus, and discover the strength to start again. I think you will relate to it a lot and that it will help you heal, I know it helped me. It's also a very fun, enthralling thriller/horror story (though it really isn't that scary) and a great read!