She snaps me first then doesn't reply to my snap. Why?

K, so there's this girl in my class who I've been snapping for a bit. One day after school she snaps me asking about how I felt in one of the harder classes we have. I responded and she opened and never replied, which is fine cuz I didn't ask a question so techjnally she didn't have to respond. Then I sent a second asking her about how she feels about the rest of the year and with a question mark too. She opens and doesn't respond. I just don't understand what's going through her mind. Usually i snap her first and from there we get things going but this time she snapped first. Note that She sent the snap at 3:30 and I didn't respond till around 8 cuz I was actually busy tho. Could she be mad are girls really that sensitive tho? I remember one time I sent a snap at 2 and she didn't respond till like 10 but I didn't really care. What do girls think how do they even think?
She snaps me first then doesn't reply to my snap. Why?
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