、。
She's shy, which makes me like her even more.
Literal
She [topic-は] shy-person is [because-から], all-the-more I [topic-は] like.
はにかみや ('shy person') uses the productive suffix ~や (屋), originally from shop names but extended to describe people known for some trait: 寂しがり屋 ('lonely type'), 照れ屋 ('easily embarrassed type'), 怖がり屋 ('coward'). The same suffix in shop contexts gives 本屋 ('bookstore'), 八百屋 ('greengrocer'). である (literary copula) plus から gives a slightly elevated 'because.' いっそう ('even more, all the more') sets up the central beat — her shyness doesn't put him off, it adds to her appeal. The whole sentence reads with the affectionate tone of someone reflecting on what makes them love a particular person.