Doesn't seem true; going with the game script if you are not on the "Others" path you get railroaded into either "Maybe in the future" or "Refuse" as responses:You don't need to be on "others" path. As long as your affinity is DIK you can have her.
Python:
if not branchAlone:
menu:
"Maybe in the future?" if True:
jump ep9_heather_maybe_label
"Refuse" if True:
jump ep9_heather_no_label