the replay gallery relies on the player having been to/played the label so we need a way to that label but make it "unplayable" but still accessible with a replay so i came up with this for you.
label start:
if love > 7:
call heart2heart
return
label heart2heart:
if not _in_replay:
return
else:
show screen Replayexit
e "all the good stuff here"
$ renpy.end_replay()
return
this lets you call the label multiple times, but still not do anything there, BUT it will unlock the scene for replay since it was (as far as renpy is concerned) 'seen' and it should play through fine during a replay
this is untested code... let know if it works.