That's what her reputation turned out like, and what TSAB propaganda likes to claim. It's not what she actually did. Let me count the befriendings:

• Alisa Bannings. The sole "Nanoha-style befriending": Nanoha punched her to make her stop bothering Suzuka, after which they somehow became friends. No starlight breaker, though.

• Alicia. Mostly Alicia was the one beating up Nanoha. It's true that Nanoha eventually defeated her in a climactic battle, after first sort-of-befriending her along more normal lines; however, Nanoha's victory in that battle isn't what finally turned Alicia. That's down to the actions of her insane, brain-damaged mother.

• Vita. Neither motivation nor loyalty ever wavered.

• Reinforce. Decided to work with Nanoha after Hayate asked her to. Nanoha's starlight breaker was helpful for temporarily weakening the defence program, but was not instrumental in the actual motivation change.

• Vivio. ...do I really need to go there?

Her reputation for converting enemies is not undeserved, but she's not converting them by defeating them; she's converting and defeating them. Amusingly, the movies (which are officially TSAB propaganda) show marginal causation where there's only correlation.

Oh, and explicitly because people have asked me not to, you're hereby invited to the rizon/#nanoha irc channel. I'm relatively confident you won't show up, which is good - it has a tendency to distract authors when I do this. :P