ELI5 MD Anderson’s employee insurance

So, my girlfriend is an employee at MD Anderson, but doesn't understand their insurance that well.

Today she ended up having an emergency and we ended up visiting an urgent care emergency room, partly because she didn't want to visit an actual hospital and partially, because we don't understand how her insurance works, I heard they had free care, but where does she go for that?

The only thing she is familiar with is employee health but that closes at 4. Where is she supposed to go for more immediate things and stuff like that?

Anyhow, anyone that has experience working there as well that can share their experience or some tips on where to go next time or the best way to use her insurance, it would be deeply appreciated.