Why does this girl ignore my texts but acts so nice in person?

I've been crushing on this girl for a while and we are pretty good friends (people think somethings up and we are close). Anyways the one thing bothering from making moves is that she doesn't repond to my texts that well.

Its so frustraing and worrysome when you send a girl a text and she doesn't reply. I mean I know my text probably didn't need a reply but STILL :(. I used to text her a convos at least once week over the summer but I stopped cause she didn't really text first but she still seemed interested. Anyways I took a long break from texting her once the school year started cause I feel awkward tryna text her at night when I talk to her everyday at school anyways. I do text her questions, not really convos out of neccesactiy and she either takes long or doesn't respond (welp sorta not).

So at school me and her have on class together and we pretty much talk when ever there's time unless her femal friend is tryna talk to her. We are close and comfortable with each other even with physical contact. Hell she wanted to form a study group with me this weekend. We share food, laugh , mess around help each other do work. And in the rare times we can't talk for an extended period of time we can talk about anything for a long while. She is always smiling, giving me full eye contact and attention and sometimes get annoyed when I ignore her.

SO WHY doesn't SHE RESPOND OR TRY AND TEXT ME :( sometimes... I know she has her phone with her a lot,... am I not important to her? :( she cares about me in person so... Im so confused. So many high fives, encouragements, staring at me for inside jokes and nothing texting whys! Someone explain?
Why does this girl ignore my texts but acts so nice in person?
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