It's hard to say who will make it to London but her main rivals will come from Russia and China. Her current bar routine is 7.1 in difficulty. If she hits she can be golden. There are rumours that she can still upgrade her routine. She can do a double double tuck dismount but can she be consistent with more difficulty? I think a 7.1 D-score is safe enough to be golden. She will have home advantage.
Here's a video of Tweddle's UB routine from team finals in Tokyo 2011. She scores 7.1 D-score + 8.566 E-score = 15.666 total.
Toe-on 1/1 + Tweddle + Ezhova + *VLW (D + F + D + E) 0.6CV
Ono + Markelov + Gienger (E + D + D) 0.4CV
Tsuk dismount (D)
3.6 + 1.0CV = 4.6 + 2.5CR = 7.1 D-Score
*VLW is my own acronym for Van Leeuwen. I'm going to make that acronym work :)