TL1 (original): Madoka teams up with Mami a week before Homura's transfer, they end up saving Homura from the barrier. For Homura, Madoka is pretty much the sourse of admiration we've seen the current Mami be to the current Madoka. Alas...
Madoka: dies, fighting Walpurgis alone. We don't know if she succeeded or the witch merely escaped. Anyhow, Homura survives it, even being a muggle.
Mami: dies in the same battle.
at least a heroic death, with her head on
Sayaka: no info, it's possible she didn't even become a PM originally.
And since Mitakihara had two active Puellae Magi, there was obviously no need for Kyoko to arrive.
TL2: Homura's a Puella Magi, still no sighting of Sayaka and Kyoko. Mami's there but seems to die again, and Madoka eshausts her Soul Gem completely, defeating Walpurgis. Judging by Homura's shock when her friend becomes a witch, this timeline had Madoka as the first matured witch in Mitakihara area. dunno if I should cry or feel relieved that it might mean Sayaka and Kyoko being spared again this time (that's not a given, of course), but here's a disturbing point: if we assume Mami met her death in the last battle... We've had THREE magical girls fight Walpurgis, including one REALLY powerful magical girl... and they were BARELY enough! Now, how the heck did Homura plan to fight Walpurgis alone, or even with the help of Kyoko?!!!!
Like someone at AS pointed, the only option would be to steal a nuclear warhead.
TL3: the most horrible. Homura tries to warn the girls, but they're sceptical, even more so with our ever-sceptical Sayaka involved and Kyoko arriving to Mitakihara for some reason. Then, Sayaka becomes a witch (details unknown, but since she had been warned about the system, it shouldn't have made an impact equal to the one we've seen - maybe she just burned her powers out this time). It sends things downhill, because Mami snaps and in her madness tries to perform what she believes to be a multiple mercy kill. Madoka... losing two of her friends and killing the third to save the fourth... in her place, I'd probably go witch on the spot.
Homura manages to pull her out of despair, but they are once again the only ones to face Walpurgis, cue another Pyrrean victory. I start getting an impression that Walpurgis and the likes of her are effective means to "havest" the magical girls who have been around for too long.
This time, Madoka herself sends Homura on a mission to prevent her convertion, whereafter we see one of the most painful moments in the whole show
TL4: Homura spends it QB-hunting, plus warning Madoka about suspicious white twerps lurking around in wholesale quantities. Now, things get a little weird due to the time skip: we see Madoka unconversed and Homura defeated by Walpurgis... but from all the other players, at least Mami should have been around by default! Did she die again? Before the Walpurgisnacht or during it? Homura was determined to fight the witches alone, however. Maybe she turned Mami down that time (or Mami caught Homura red-handed over her fluffy friend's
uneaten corpse), and then... no info. The ending is also a head-scratcher, with Kyuubey saying that Madoka has defeated her biggest enemy and has no other outcome but to become a witch. Has she already become the witch or is it his pseudophilosophical rant again? Probably the former, though: if it had taken Madoka all her powers to defeat Walpurgis with the help of Homura [and Mami?], the outcome of her fighting alone is a no-brainer.
So, the current timeline (TL-friggin-5!
): Homura has obviously given up on everyone except Madoka. Bad news: Homura was witnessed to kill a cute creature AND Mami's friend before getting a chance to explain (or, rather, she had gotten one... but she chose not to spill the beans in that school corridor, maybe out of fear to mess things up again), Sayaka also had the first impression of her as someone threatening Madoka... where's mah reset button! But Homura is determined to use this timeline to the full extent, regardless of how things proceed.