[TnAdct1]

If you want my opinion (and this is from someone whose only seen episode 5 of the series, although he's following the episode summaries), I think one of the biggest problems with Homura's attempts to stop this is her way of doing it, more specifically her:

1. Not trying to actually befriend Madoka and Sayaka upon arriving in this timeline;

2. Considering Mami and Kyouko to be lost causes from the start and siding against them.

Face it, even if she's a time traveller, that doesn't mean she has to keep everything to herself and not make friends. After all, look at Mikuru from Haruhi and Chao from Negima.

That is why I feel that Homura should just consider this timeline to be a lost cause: no matter what's going to happen, this is going to end up as a "bad end". However, if she enters a timeline similar to the current one and not act like a jerk, she can fix the mistakes that she made in this one. Among the tips:

-Once transferring to Madoka's school, actually attempt to befriend her and Sayaka.

-Ignore the fact that Mami and Kyouko have made contracts with Kyubey and work together with them (while ensuring that not only they have enough Grief Seeds in preparation for Walpurgisnacht, but that neither of them die or become witches until then).

-Inform Madoka and Sayaka about the truth when it comes to Kyubey and being a mahou shoujo (once they've gotten to know each other better but before Sayaka becomes one), and make them promise to keep this a secret from Mami and Kyouko.

-Aren't there any other mahou shoujos in Japan besides those five? If so, try to contact them and inform them about Walpurgisnacht so that way there'd be more than just her, Mami, and Kyouko fighting (as well as someone who can take care of the mahou shoujos who end up becoming witches in this attack).