Considering her comment this chapter... I think it is confirmed it actually happened for real. Not just some non-insertion (or non-contact) stuff, or she would not comment on it not having hurt.
Girl is a criminal~ (would've been either way, really) Though tbf, at least her victim was someone constantly propositioning that exact activity to her, so on a scale of without consent to against their will, it is very strongly to the former and far from the latter. Doesn't make it ok, but it's to the extent that if I were the victim [who constantly propositions to and adores the perpetrator] I could probably forgive her - but her being so tsun afterwards and overall keeping it secret does make it uncertain.