I disagree, I think one in a trillion sounds extremely generous to Melania, and the actual probability might be lower. For her to use so many of the same words/phrases, and especially in the exact same order, should make the calculation of the probability tip into pretty extreme values.

Like, if I flipped a fair coin 20 times and got some configuration of heads/tails, the probability of you getting the same configuration (ignoring the order you get them) is about 12.5 percent. But if you flipped them and got the same order as me, that'd only be .000095% - the odds went from 1 in 8 to 1 in a million. (I think I got all that right, but I'm doing this on the fly).

Now replace a coin, which only has two outcomes (I chose a very simple example to mimic a "generic subject matter"), to the probability here. Choosing that specific topic to discuss, choosing the specific diction/syntax, and even using similar turns of phrase, would probably result in a very small probability of it being a coincidence even if she didn't give all the same sentences in the exact same order as the original speech. Having the two speeches play along side each other perfectly would then plummet the odds to insane levels. In fact, the article even mentions that the one in a trillion was for a less extreme example than the Melania speech.