left on seen accidentally?

The conversation was going great like we were joking and we have similar interest like reading books and stuff. We are friendly and for the most part she doesn’t respond for the few hours and I don’t mind that at all because I have my stuff to do and she goes in rly hard high school so she also have stuff to do. But today for the first time she left me on seen and I think it was accidentally because she usually takes much longer to respond and it was fast after I send the messages so I think she accidentally clicked on it and maybe forgot to respond or she will later. As I said I don’t mind and few times it happened to me to that, bit I just wanted to ask, would it be stupid to send just a question mark after being left on seen