I couldn't tell if she was socially awkward or crossing boundaries. Am I wrong for cutting her off?

During college, I organized literature workshops for extracurricular credit. That's where I met a peer I'll call Grinch. At first, nothing seemed unusual. She attended some events, we talked occasionally, and I assumed she was trying to make friends. Over time, though, she became increasingly focused on me and my friend group, interrupting conversations and even classes with unrelated comments. She tried to join almost every interaction, and seemed to mistake basic politeness for friendship. Instead of telling her directly that I wasn't interested in becoming close friends, I stayed polite and hoped she'd eventually get the hint. Around that time, I started dating Small Witch. We kept our relationship private at first, although we had a few inside jokes that probably looked odd from the outside. When we finally announced that we were together, Grinch said she felt "betrayed." She also said she thought I was interested in another university peer because of the way we joked around. That completely caught me off guard because I'd never shown any romantic interest in Grinch. After my relationship became public, she started interacting more with Small Witch as well. She made comments about our relationship and, after seeing one of our playful exchanges, said something like "Now I know how this relationship is going to end." Individually, maybe none of these things would have been a huge deal. Together, though, they formed a pattern. That made me and several of my friends uncomfortable. The biggest incident happened in a hallway. She came up behind me and, without asking, brushed dust off my back and then my butt. She said she was just cleaning plaster dust off my clothes, but I felt extremely uncomfortable. Other people in our circle started distancing themselves too. One friend even blocked her, and she apparently found another way to contact him anyway. Throughout all this, I kept trying to be patient because I genuinely couldn't tell whether she was being manipulative or if she simply struggled with social boundaries. Because of that uncertainty, I gave her the benefit of the doubt much longer than I probably should have. Eventually, I spoke to her privately, explained that her behavior made me uncomfortable, and said I didn't want that level of closeness anymore. She denied having bad intentions, said I was misinterpreting everything. Insisted her comments were just jokes. After that, I blocked her and moved on. Years later, I heard through mutual acquaintances that she had found a different friend group and, allegedly, was doing well. I honestly hope that's true. Looking back, I think my biggest mistake may have been waiting too long to establish clear boundaries. I was trying to be compassionate because I thought she might simply have poor social skills. But in doing so, I let the situation drag on longer than it should have. So, am I wrong for eventually cutting her off, or should I have handled that much more directly from the beginning?