After leaving school, Arianna drove herself home in a happy mood as she had just gained a new friend or more of a sidekick. Arianna lacked friends so she didn't mind having more than one.
She only has Freya as a friend who also has her other friends whom Arianna rarely talked with as they have nothing in common. Arianna wasn't the type of girl to play with others simply because her friend is playing with them.
The "Arianna" before was easily pressured but she who had been through a lot, wasn't one to easily fall for other's tricks. She was someone who would rather go down with her enemy than let the enemy win.
Since there was no harm having Esther by her side, she didn't feel any pressure. And Arianna didn't want to drive herself crazy with the exams coming and with her engagement on the way.