I think Ending 3 is bugged. If you read the final note right after talking to her, instead of giving you the option to say what the note tells you, it just displays the text "She is done talking."
This makes it impossible to reach 100% affinity (love, affection, or whatever the pink meter is called) and trust the scientists.
And even if you do everything perfectly to get Ending 3, because of this bug, you always end up getting Ending 6 instead.
(or well i think this is a bug, Maybe i'm just doing something wrong and softlocking myself from ending 3
Bugs aside, This sht is FIRE fr fr, I love the kind of woman that will actually just kill me