Honestly with how dramatic and "B-movie" the story is, I genuinely don't think we can really trust Alice yet. Her "aw shucks I'm just an innocent country girl" demeanor could either be an act or be genuine but still hide some dark side. That entire family is super weird.
One thing that reinforces that feeling for me is the whole situation with Mei. She and Alice contradict each other about what happened at the pier, and while it obviously much more likely that Mei is a liar, there's still something weird about Alice's version. I don't know what Mei's deal is so it's hard to judge for sure, but there are not many scenarios where I think she's genuinely ok with directly letting the MC drown, in which case the idea that she was going to let it happen is hard to believe. Her seeing that Alice was going to intervene makes sense. Alice also has a very easy-to-understand motivation for lying, which would be to undermine a rival for the MC's affections.
Summer is the only character I feel genuinely confident isn't hiding something.
TL;DR: Mei is 99.99% lying about the pier, but I would not be surprised if Alice was also lying. Alice may also have a darker side that she is hiding behind her innocent attitude.