Mahiru seems to be nothing more than a political pawn for her parents, if anything. We can see how Amane's presence is like a light at the end of the tunnel for her, which then makes more sense why she's so aggressive in trying to court Amane. By getting into his family, she can eventually completely remove her parents from her life, and it would also prevent her parents from trying any tricks (e.g. superficial "love") to try to manipulate her.
When she woke up from her nightmare, the first thing she saw was her future hubby. Come on Amane, gotta give your future wifey a hug to put her at ease.