Boil Water
Without a doubt, this tweet can make anyone think that the girl was planning on pouring the boiling water on her boyfriend who she discovered was cheating on her. But thankfully, that was not the case, she just suggested boiling the water for a long time before making the tea.
We understand that this was perhaps a metaphor to deal with the news of her cheating boyfriend, but we suggest that she should take some time to calm herself. Once she is calmed down, maybe they can sit down and talk about what happened.