When should I follow up with her if she asked to reschedule a date?

I was supposed to go out with a girl from college on Friday. She had some work come up and asked to reschedule. I asked her if next week same day/time would work right after she asked to reschedule and she hasn’t replied yet (2 days now). We’ve only gone out here and there so it isn’t anything serious yet, but she’s never not replied to me, and has never cancelled. How many days should I let go by before following up?
When should I follow up with her if she asked to reschedule a date?
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