Should we take a photography discount that depends on public wedding photos?

The photographer's quote included a $350 reduction if she could use a selection from our wedding in her portfolio and social posts. My partner said, "That's the flowers paid for." I nearly agreed.

One of our guests has already asked us not to put recognisable photos of her online. She is happy to be in the private gallery. We haven't promised anything beyond saying we'd discuss it with the photographer, and we haven't signed the booking agreement.

When I asked about excluding her, the photographer said she could work with a clear list for posed portraits but didn't want to promise that a guest would never appear in the background of a crowded dance-floor image. I appreciate her saying that before we book.

I'd be comfortable with the photographer sharing one portrait of just the two of us. My partner would like her to share the party as well. We can pay the higher quote if we trim something else, but we haven't checked what its publicity terms say.

How do we decide whether a narrower arrangement is worth asking for? I want our guest to hear a clear answer, and the photographer to know what we're agreeing to, before a discount becomes the reason we make promises neither of us can keep.