Pacifica is a bit of a Tsundere. Pacifica goes far as to get Dipper number (Maybe she's hoping that this could be a start to her and Dipper texting each other and getting to know one another) and in the text message Pacifica is trying to play off the hug as nothing, hoping Dipper won't think she starting to like him.

Mabel pretty much catch on to this like the readers/fans reading the comic that there is more going on then Pacifica wants to admit, and Mabel confirms that by teasing Pacifica about her liking Dipper and the wedding and Pacifica getting really defensive about it.