I always smile at this scene, Nanoha's nickname "The White Devil" aside. It really shows that you are a badass Magical Girl when a centuries old Combat Program (in the form of a cute loli but still...) calls you "Devil".
The second Sound Stage to Nanoha A's added an extra twist to this scene. Reinforce after meeting with Hayate in her dream utters the following line
"For my gentle master or for the devoted knights... isn't there a way to save them? The Blazing General... Knight of the Lake... Azure Wolf... Scarlet Iron Lord... and our Master Yagami Hayate... It can be God or the Devil... Please, someone, save her."
Isn't it amusing that the one who saved her beloved was called "Devil" by one of Hayate's knights ? Could it be that Vita somehow, subconsciously Knew that Nanoha can save Hayate ? You know... we could stretch this line of thought a little bit, Fate is a Lightning user and can summon lightning up from the sky, like a God of Thunder, like Zeus for example, even one of her attacks is called "Zeus Zanber".
Be Happy Reinforce-san, the God and the Devil came to save your beloved Master ^^
[Sighs Sadly] If only they could save You. I still regret that Reinforce had to go away. Oh I know that Reinforce Zwei came to replace her but... but it seems kinda unfair, that after all those centuries of tragedy, grief and unhappiness Reinforce couldn't live happily with her Master, it just... doesn't sound right
[his heart of a yuri-fanboy burst into flames and a sly smile appears on his face] Not to mention that Hayate and Reinforce would make SUCH a Wonderful Couple.