Looked up the kanji on the missing text and came up with その願いを胸に ほむら 魔法少女になるのだった to
With that vow held to her chest, Homura became a magical girl.
I'm no translator, but a guess-translation is better than leaving it untranslated forever, specially since is the last thing missing in the pool.
I will protect MadokaWith that wish in her chest, Homura became a magical girl.Ugh... ughhUwahahahahahaaaI'll stop being human! Kyubey~!Magical Girls - Those who fight witches
Madoka loses her life after fighting a powerful witch