How much time between when she sends the text to when I open it is good?

Like I don't want to seem clingy or like I don't have a life or anything. Like when we were at a party she seemed to really like me whether as friends or more. She plans to get together to hit the club with me when I turn 21 (I will be 21 in August), so I don't think she doesn't want to link up. But she texts back after a whole day and I respond after a few hours. To me, the only reason I don't text back is if my notifications are off on snap, busy with work or family, or my phone isn't on me because I am playing basketball or something but I usually text back within 10-15 minutes at most.

How much time between when she sends the text to when I open it is good?
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