I set up a date on Sunday for Wednesday at 4

So she texted me today: "Hey I'm really sorry but my psych test got rescheduled and I have to take it later today so I can't get coffee"

When should I contact her to make new plans? This is her first flake and Id like to give her the benefit of the doubt.

Should I text her something today like "No worries, I had to do (excuse) anyway"