she thought that Aqua will take her if she told him she loves him just because of her power. So in the next chapter she will try to hurt Tiara, but like in any otome game she's being saved by Aqua. Aqua then tell her that he wants the holy maiden power but he think that Akari is a pain and all he need is Tiara alone, upon hearing that Akari have a mental breakdown, but later on in the story she got her redemption by preventing the sequel heroine from disrupting Tiara and Aqua's wedding. Oh yes, despite that Akari tried to hurt Tiara, Tiara still forgive her just because she's an isekai-ed otome game fan