Edit : I'm not one for tricks or playing games, but I'd not tell her you chatted/sexted with her at first.
It's also one of the times I think it's okay to be a bit sneaky.
I recently went on the "cheating" dating site Ashley Madison while gathering information for my e Book on online dating. For over 12 years now, this website kicked off a boom of dating sites for people.
I even went to the point of chatting and sexting with her, but never got to the point of meeting.
Actually, I wouldn't even say you know her profile is active.
I found out through her browsing history that she uses this dating/sex site. It's irrelevant if she meets people or not tbh. It's possible she only wants the attention, but still. It can be hard to be objective on whether person you care about us lying.
I even made my own profile and started checking her if she logged in or was online. There's better and more appropriate places to do that.