Should I give up because she seems less interested?

Anonymous
There’s a girl I know at school (we’re both 18) who caught my eye that is pretty shy and quiet.

I initially noticed she glanced at me all the time along with her friend, who I know well. She seemed pretty nervous in situations where I tried to approach and would either turn to her friends or just be really quiet.

This went on for a few weeks until spring break came up. This meant I couldn’t really see her for a few weeks so decided I should try messaging her on Snapchat.

I chatted to her for a day or two near the start and she seemed really responsive.

She then went cold and has been like that ever since, replying back every two days.

Her replies aren’t fast but they seem pretty enthusiastic and it’s not like she’s trying to stop talking to me or anything. They’re just slow.

I’m unsure about how to continue this situation as I’m unsure why she seemed so interested in person (at least for a shy girl) but then it just slowed down.

Any advice on what has happened and what I can do moving forward?
Should I give up because she seems less interested?
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