Ok, I'm going to say something here that hasn't even been considered (I think). What if the OP's depression isn't something that can just be dealt with? Some people suffer from it for their entire lives, even while going through therapy and on medication. If the OP were to wait until he was all better, then he may be waiting for his entire life.
Now...if I were in your position, liking this girl and she liked me but she was afraid to hurt me, this is what *I* would say. "Listen...we like each other. That's been established. I understand you're afraid of hurting me and I may decide to take drastic measures. Thank you for considering how I feel about this. It means a lot to me, and proves to me that you're the kind of girl I want to be with. I'm not telling you not to worry, but it's my chance to take and I'm aware of the possible outcome. I'm still willing to take that chance, and I hope you will be willing to take it as well."
Just me, though. Take it or leave it.