You're referring to scissoring, which is actually not very popular (for a lot of reasons) and given the line in the chapter referring to "being the one who had it done" also not what happened here. What probably happened was fingering, which is typically penetrative and would count for many definitions of "not being a virgin any longer". But there are other explanations too (being eaten out, for example), and those are also debatable as to what traditional "virginity" status would consider.
Also a comment like this on a yuri manga is just going to invite loads of debate, in case you weren't aware. I've read multi-page forum discussions before that have people pulling definitions for "virgin" from every dictionary and culture they can possibly find, and it's just a mess of an argument. But if your definition is "some kind of penetrative sexual action", then fingering would probably be sufficient and has a good chance of being what actually happened here.