I vaguely remember seeing this movie sometime in the mid-2000s, though it may have been a 1990s-early 2000s movie from what I remember of the screen quality.
There’s this woman who returns (with her fiance/boyfriend?) to a childhood place, where there’s a lighthouse home (I think?) overlooking the sea. And she’s initially scared of her former childhood friend who lives there, because her mother claimed that when they were children, he tried to seal a pact with her using a knife and their own blood.
But later on in the movie, it turned out that her mother lied to her – she had forcibly separated her from her childhood friend after she saw them seal a promise with a kiss. But somehow, she had manipulated her daughter into seeing the guy as a threat by lying about this memory. (I’m guessing she just didn’t want them to be together?)
Also, the woman’s fiance/boyfriend turns out to be a complete asshole, as he had cheated on her with one of her girl friends – that friend ended up pregnant, not to mention remorseful (as she has a boyfriend of her own whom she loves very much, especially after seeing how sweet he is to her), so the woman’s friend tries to hide this secret. However, it gets revealed in the climax of the movie since the fiance/boyfriend sees the main woman kissing her childhood friend, then in the climactic fight the woman’s now-lover beats up the low-life fiance/boyfriend and has him thrown out. In the end, the woman’s friend ends up staying with her own boyfriend, who accepts the unborn child. And the two main characters end up together as well since the whole childhood memory misunderstanding is cleared up.