"you created a paradox where the original timeline cannot logically exist" Except it CAN exist. The thing about Stable Time Loops is that they're... well, pretty stable. See also: "You already changed the past"
YES ! Finally someone ( or somepony, I'm not sure ) notices this ! The time-travel episode made no sense ! The only reason Twilight became future Twilight was because future Twilight travelled to the past and got her upset, in other words she's the result of something that she's the cause of, it doesn't add up !! And so once again, doctor Whooves has to set out to fix things. Way to go Twi, you got your dimention destroyed. Of all the ponies in town, really...*sigh*
Actually, by creating the loop, she was able to go back in time . Lets say that your future self appeared in your room right now. At that point, you're forced to go back in time if you want to live.
If however, you went back in time without doing it the last time you reached that point in time, you are screwed. It's confusing, I know. Paradoxes are the main reason i keep breaking people's attempt at time travel.
I don't recall a paradox being created, from what I saw, Future Twilight told herself how to find the time spells. Future Twilight knew about the time spells because she had been visited by her future self. Past Twilight failed to deliver the message she needed to just as Future Twilight had, thus creating the problem of what was to come and leading to finding the time spells. Unless I am missing something in the episode, no paradox had been created. Also, aren't paradoxes an impossibility because time is written in stone?