Sweetheart, killing yourself is not going to solve anything. Think about it: you argue that because you're an 18 year old lesbian that you will never, supposedly, get a girlfriend, or perhaps even a wife if that is what you want one day, well, to be honest, how do you know that? The answer? You don't. It's an assumption, & a false one. It seems to me that it may be your depression, NOTHING in reality, that is telling you & thus making you think that you will allegedly never find love. You can beat this. You can overcome this. Join forums & chat with other lesbians. Try to Google things that you can use to your advantage so that you can find love.
You're a beautiful person who is very young & has their whole life ahead of them & I can honestly tell you that it's very important that you live it! There is NO evidence to support the idea that you will never, supposedly, find love with another beautiful woman.
Don't let the lesbophobes win! Carry on & be the strong woman you are!