The OP has said nothing about her child liking Disney dreck.
She has said that her child cringes at romance/kissing.
You have no reason to assume the OP has allowed Disney movies.
Jane Eyre and other classics are taught in school to older teens, aged 14-15-16. This is because a great many younger readers don't have an interest or the vocabulary or the understanding of social nuances in the historical context to really understand such novels. A great many teens of 16 don't either.
Al the books and the play you mention involve relationships. So do the works of Beatrice Potter. Relationships are not the central theme of each one all the same. In some, relationships feature prominently, but from an emotional rather than a purely sexual pov, and importantly for a young, heterosexual girl, some are narrated from the pov of the female protagonist. In some, relationships are just assumed. In some, they're a secondary or tertiary theme. Relationships are a key part of the human experience. They are common to us all. They can be platonic and they frequently are - people generally have more friends than lovers. And people can be asexual... What you saw in those books may have been just heterosexual relationships or relationships in general, but others may have been fascinated by social class, the theme of conscience or evil, the fantasy and escapism, conflict between specific characters, the plot and the exciting conclusion. Some slogged through all of the literature you mentioned in school, while wishing they could be reading novels about war or 15th century Japan or Hell's Angels or biographies of the kings and queens of Denmark.
The inclusion of explicitly sexual themes or themes relating to sexuality, sexual identity, or gender identity are new to literature aimed at teens, which is what the OP asked about. As a pp remarked, these things come in waves. Nobody is obliged to hop aboard the latest bandwagon.