While I can't speak for everyone that plays her, I've seen a few on FG that assume she's good against campy characters (the reason I think some people pick her against me since I play mostly campy characters) because they think they can Nayru's Love spam and win. If you face people like this, then limiting your projectiles and surprising them with close range can work to your advantage. That's almost always how I play Samus against anyone with a reflector.
That said, any good Zelda won't do this and will still try to force you to approach her using Din's and Phantom. In this case, I imagine it would be a game of patience where you, as Duck Hunt, are perfectly capable of out-camping her. Stay out of range of Phantom and she'll throw Din's, stick closer to her and she might be prompted to approach you since Phantom is super punishable if the opponent is at mid range. While I don't know how punishable DH is at mid range while using projectiles, I think he's better off than Zelda. Maybe jumping up and dropping the can on her head and landing with down-B might be advantageous for you. If she reflects the can, it'll go straight up, harmless, and it'll leave her open to the down-B shot. Just a thought as I don't know DH. Basically, like everyone else said, if you force her to approach, you're already at an advantage. Also, never, ever spam projectiles at her while she is off stage. She will take advantage of the endlag on these moves and FW you to death. Always be aware and safe while you're in FW range especially on FG where people like to overuse it whenever they think you're vulnerable.
Best of luck to you sir!