I empathize with Mari's honesty. You can lack awareness because an parental figure continually presses for the truth; telling the 'truth' is suppose to appease her mom. Mari lacks confidence or is self-conscious because it's possible that pivotal moments in her life have been decided for her. Her preference for serious guys seems to be molded by her mother concerns for her, but Mari's burdened because her only concern would be finding a partner that her mother can accept.
Mari doesn't have room to be vulnerable; she's a conservative girl who passes off as a fashionable extrovert. Her social circle is small and she doesn't seem to have any confidant. She overcompensates with an impulsive truth to make up for her repressed feelings. Mari seems mirthful of her background, so there's also the short answer of her mom falling for a flashy guy, hence her preference for the polite and kind type. (We don't know the full story of her parents, but the first few pages imply that her mom is sharing the burden of her emotional baggage to her daughter.)
tldr: The dynamic is changing, and the two have a shot for a genuine romantic relationship.