It has nothing to do with being in college — and everything to do with whether YOU declared her as a dependent on your 2018 return! That’s what they checked first. And if her SS# appeared as a dependent on your 2018 return, they passed her over.
If she filed her own 2019 return and was NOT a dependent on your 2019 return, she might have a chance next year, when she files her 2020 return, to dispute the lack of a stimulus check for 2019, and claim it on her 2020 return. We will see what they decide about those situations.
Now, if you did NOT declare her a dependent in EITHER year, then she still has a chance of getting a check based on her own 2019 return. That would come in the months ahead.