Is it ok for my girlfriend of 3yrs not to tell me who is messaging her on telegram?

Recently, I found myself in a confusing situation. I noticed on her screen that someone was messaging her on the Telegram app early in the morning, which I didn't know she even has. As far as I know, it's like WhatsApp, which is highly secure and auto-deletes messages. So I got the app and saw that she was online one morning. I wrote to her good morning that day, and she got mad when I asked about it. She says it looks like I'm stalking her. I told her if I was stalking you, I wouldn't have said good morning to you on the telegram app. She says she didn't feel she needed to tell me everyone she talked to. I agree with that. However, this looks shady to me. Why not just say I'm talking to bla bla bla and put an end to this? I really need your perspective on this. I think she should tell me if there's nothing to hide. What do I do now?

Is it ok for my girlfriend of 3yrs not to tell me who is messaging her on telegram?
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