I deal with this a little in my new article. I’d see your sister as lesbian, clearly. Rubbing another body doesn’t establish sexuality.
Of course, being a Tantric sensibility, I would say that our thoughts move energy and even to sit with someone in a state of openness and happiness is essentially a sexual exchange. The person you’re happiest with or who has deepest entrance to your inner being is, essentially, a lover.
The point you’re not yet dealing with is your sister being punished by a theological system that made physical expressions of intimacy all but criminal, and disallowed sexual teachers who might’ve helped guide into higher practices of sexuality.
So, amid the fallout and punishments, she ends up being a celibate lesbian. Good for her. Lots of people killed themselves.