When the mc turns Jill down for Sage he makes it obvious it's a girl he's going to see:
mc: "I'm so sorry. You caught me at a bad time""
mc: "I made a promise to a friend to come help her."
mc: "She's sick and needs someone to take care of her."
When they arrive at their picnic destination:
Jill: "We're here!"
mc: "I have no clue where here is."
Jill: "Here is where we will have your birthday picnic!"
mc: "A picnic? What a surprise!"
So yeah, definitely Jill knew it was a girl he was blowing her off for, and she definitely planned the outing for his birthday.
She was a little caught of guard but pleasant when he told her he had other plans:
Jill: "Oh... Yeah, of course. I understand.!"
Jill: "I didn't plan anything big. It was spontaneous.!"
Jill: "You're allowed to have other plans. Haha...!"
Jill: "So, uh. Happy birthday.!"
People's emotions are what they are. You can rationalise "It's fine, I didn't tell him about this in advance", but that doen't mean a person won't be upset when their efforts are for nothing, particularly if another girl is involved.
And as I keep saying, she didn't decide to dump the mc because of it, but it affected their relationship a bit, and unfortunately that snowballed into them eventually breaking up.
The only thing related to Schrodinger's theory here is there is pussy involved.
The two quotes are related but not contradictory.
Jill didn't directly dump the mc because he didn't go on the picnic with her. Going on the picnic set off a chain reaction of events that lead to the strengthening of their relationship:
- The mc confessing to Jill that he was falling in love with her in the picnic rains sequence.
- The mc redefining the terms on how they would handle Tybalt's blackmail in the same picnic rain sequence.
- The Balcony climbing scene which left Jill wanting more.
- The morning run with that lewd display in/by the river.
- The visit to her friends.
- Jill's decision to lose her virginity to the mc.
Not going on the picnic derailed some things:
- The mc didn't confess his love to Jill.
- The mc didn't tell her he was going to see her regardless of Tybalt's blackmail.
- The balcony climbing scene left Jill feeling something was missing in their relationship.
- The morning run didn't happen, therefore Jill didn't take the extra step of almost touching the mc's cock.
- Jill decided not to invite the mc to meet her friends.
- Jill will remain a virgin for life.
It's "Sliding Doors" man!
The point being, that Jill didn't end the relationship
just because the mc didn't go on the picnic.
That doesn't mean she was a peachy keen Jilly bean when he turned her down. It's only natural for her to be disappointed.
So to those who are saying she was a hypocrite for getting upset when he turned down the picnic invite, it's only natural for her to be upset after excitedly putting in an effort for the birthday celebration with her guy, only to be turned down by him because he's off to help another woman.
And to those who are saying Jill dumped the mc because he didn't go on the picnic, there's way more to it than that.