She first met him at that party all those years ago.
Pacifica didn't really know much about Dipper Pines, apart from his twin sister and carnival barker uncle. Her low opinion of Stan and Mabel had given Pacifica the image that he would be exactly as his relatives were- idiotic and childish, not worthy of being in the company of the Northwests.
How could she have been so wrong?
After watching Dipper take down a ghost almost singlehandedly, her opinion of him rapidly changed. He had gone from being "one of the Pines" to "the okay one of the Pines".
And then the end of the world came around.
Not only had Pacifica found out about her family's allegiance to Bill Cipher, but also that Dipper had made that appearance back in her life. She considered him to be the best member of the Pines family by that time. When he stopped the end of the world with the help of his family, Pacifica knew that she most definitely liked Dipper. But she wasn't sure in what way. He was cute, but not in that way.
And it was after he had gone home that Pacifica really started to miss him.
Dipper became a casual thing in Pacifica's mind. Thoughts, daydreams, middle-of-the-night fantasies all came flooding to her in a matter of months. And Pacifica eventually had to face the truth that she, Pacifica Elise Northwest, local rich girl, had developed a crush on one of the town heroes. She kept it a secret from everyone- her friends and definitely her family.
But it soon became hard to hide once he had strolled back into her life.
The crush on Dipper festered in her mind for months. This, coupled with the challenge of being a "normal kid", had given Pacifica a conflict she could never resolve. But they would probably never meet again. She continued to think that until she saw the Speedy Beaver roll into town again after a year- carrying a slightly older Dipper and Mabel. She and Mabel bonded quickly after reuniting, and Dipper tried to avoid her as best as he could. It wasn't that he was insensitive, it was just that he was really awkward and didn't really know how to approach Pacifica. Normally she would see him with some other guy- a man she soon knew was called Ford. Pacifica caught glimpses of them, usually Dipper running after Ford's heels as they pursued something of the paranormal. She saw the way Dipper was around Ford. Dipper was in awe of the man, though Pacifica was never completely sure why. All she knew was that she wanted Dipper to look at her like he did Ford now.
And it was while Pacifica watched the two sprint into the woods that a confession came out of her.
Mabel was nosy. Pacifica learned to tolerate it, even like it at some times. But when Mabel asked her why she constantly kept staring at Dipper while running away with her uncle, it was almost as if Pacifica had forgotten to speak. She stumbled over a half-baked explanation, saying that something caught her eye and she just happened to see Dipper over there. Mabel saw through that lie and immediately jumped to the conclusion that she liked Dipper. Pacifica grumbled something or the other about her being right, and Mabel seemed completely overjoyed at the thought.
But when Dipper and Ford didn't come back from their trip, people began to get suspicious.
Pacifica's crush had led her to think the most extreme of things that accounted for Dipper's absence- he had died, something got him out there, maybe Dipper just vanished. But she often reassured herself that Dipper and Ford probably got lost or they're delayed. Monster hunting didn't run on their time, Pacifica told herself. They were probably staked out in the woods, waiting to capture a picture of some urban legend.
But finding Ford dead in the woods was not a promising sign.
The pictures of his body in the newspapers were not pleasing- his skull partially exposed, blood staining his trenchcoat and mangled sweater, long gashes covering whatever exposed skin he had. Whatever had gotten Ford out there most definitely killed him. The town was in a state of distress, and the concern for Ford's companion grew, as he had not made a reappearance yet. Pacifica thought the absolute worst for her crush.
Weeks passed, and nothing.
Pacifica's mind was on edge, especially after attending Ford's funeral. It made her wonder if she could be sitting at Dipper's funeral soon. What would she do then? Pacifica had to stop worrying herself into literal sickness and dreaming up every awful scenario the darkness of her mind allowed her to conjure. It was hopeless. Pacifica was sure she was going mad.
That is, until the police found him, half alive.
Her heart was overjoyed, knowing that Dipper was alive. He had to be hospitalized, and the doctors were sure he had slipped into a coma, but no less he was alive. Stan, Mabel, and just about everyone else came to visit Dipper frequently, and out of all those people, it was Pacifica who would stay the longest. She held Dipper's cold hand, hoping that somewhere in there he could acknowledge the contact.
And it would seem that he had.
Dipper woke to Pacifica holding his hand, asleep in a chair next to him. He wasn't completely conscious, and his body was craving sleep, but as he rested his fingers interlaced with Pacifica's, giving it a tighter squeeze. The contact woke her up, and needless to say Pacifica was happy.
When Dipper was totally conscious, she began talking to him more.
It turns out they had more in common than previously thought. But it was not fun discussing Ford's death with him- Dipper shed quite a few tears that day. She didn't blame him, but rather held his hand the whole time. It was all she could do to comfort him.
And then there was the kiss.
Dipper got discharged from the hospital a week later. He was somewhat shaken from hearing that Ford died, but it was mostly Pacifica that lifted his spirits. She became something of an anchor to him. Pacifica was glad to play that role, and one day just couldn't stand it anymore. She leaned into Dipper for a kiss. It was short and chaste, but it marked the beginning of what was surely going to be an awkward relationship. They agreed to not begin anything while Dipper was still in a slump from mourning. His life was progressively getting better and worse at the same time.
But three months later, a relationship formed.
Pacifica was on Cloud Nine; the object of her affections was dating her! It was an awkward first few dates; Dipper's social skills were way out of whack. But he got better and better, and eventually the two became the orthodox couple. While not perfect, Dipper and Pacifica were happy for the most part. Sure, Dipper sometimes had flashbacks of what happened to him that caused Dipper's coma and Ford's death. Sometimes Pacifica got greedy, an echo of the way she was raised. Sometimes they argued and disagreed. But overall, they were happy having begun what they did.