"Those who cannot conceive Friendship as a substantive love but only as a disguise or elaboration of Eros betray the fact that they have never had a Friend."
CS Lewis, 'The Four Loves'
If you start learning about certain religions you start to develop a sense of proper categorization...
In the west Christianity & Judaism are the mainstream options.
In the far east there are several other options.
Because imagination is generally more alluring then reality; I think it's because we tend fill in the blanks with what we consider ideal or what we want.
It's possible they didn't use female honorifics in the last chapter; it's possible the default ones are also the masculine ones but I haven't memorized the honorifics yet.
In Washington state as an example no-one is accountable for the situation. But our consent laws are tiered and complicated and I last learned about them 15-20 years ago in freshman health class so I only remember the abridged version. Basically assuming neither one is unable to ever consent...
Considering a spouse can command a demon to leave their significant other by referring to their exclusive rights to their husband/wife; kinda yeah.
If you ever have to use this, do note that if whatever sin let the spirit in isn't settled, the entity will return and be more difficult to deal with.
Generally it's a wash. They are both kids and therefore not fully accountable for their actions. It would probably depend on the jurisdiction though, so results may vary.