While in the Swamp, it seems to be possible to reset your relationship with Delphi by re-doing the quest where she asks for wogen-weed. This is due to the helpingdelphi flag being set to "flase" rather than "false" on line 7687. For existing saves, a Twine save editor can be used to circumvent this issue.
NOTE: This appears to be fixed per v0.24.0 changelogs, though public build is on 0.23.2 as of time of writing.