~*~Please help me~*~

I'd have to say yes, most likely, it would come out two different shades. The hair that's already lighter would probably go really white rather than blonde, since it's already been lightened once. And if you try to dye over the mistake, the lighter parts will still show up lighter, as they'll be starting from a lighter shade than the rest. Probably safer, whichever way you wanted to go, to go to a professional. This sounds like a bigger problem than you can fix on your own.
Okay, that was the responsible advice. Speaking for myself, when I really screwed up on blonde streaks once, I just put on a hat and bought some brown dye at the store. But I tell you, no-one will ever recommend that. I'm just really, really irresponsible with my hair. *laughs* Some of the things I've done, it's a wonder I have any left :-P .