College prof here, though I teach grad students mostly. (At a large uni.)
Nothing the OP says strikes me as out of the ordinary. Is your daughter a little flighty, or has she done things that make you feel she’s not on par with other 18 year olds? Because a lot of 18 year olds don’t act their age.
Since she’s not working, I’m wondering why she has a car, though. If we had our druthers frosh wouldn’t be able to have cars, both because of parking and because of the trouble 18 year olds can get into around the city (DUIs, accidents). We’d also rather they find their entertainment on campus, where we like to think it’s relatively drug and alcohol free. If your daughter has issues with drugs and/or alcohol a car is a very bad idea… and if she has friends with issues with drugs and/or alcohol, that’s bad as well.
I think you might need to have some role playing scenarios. How will she handle kids that want to be her friend because she has a car… and little else? Frosh tend to think that someone they’ve known for 10 minutes is a lifelong friend.
Regarding the grades, I think it depends on a few things. First, what’s her major? I’d expect a 3.0 from a high-achieving kid taking courses in liberal arts and the natural sciences… if she’s in a hard science or engineering major it might be harder. 18 hours is a lot. Personally, I think first years students should take between 12 and 15 hours, because they need time to sleep, work, get to know the campus and community, and get involved in campus life. 18 hours makes that pretty hard, and there’s the danger of the whole “hey, I work hard, so I party hard” mentality to emerge.
The other thing that might be wise if you feel she is a little immature is to give her an allowance biweekly or monthly, like a paycheck. She’ll have to budget then, and that might teach her some responsibility.
Is she good handling a schedule, studying, postponing partying and having a good time until work is done, etc.? A lot of “naturally” smart kids struggle because they were never really challenged in high school. Regardless of how well your kid knows her topics, if she isn’t super organized that 18 hour courseload could be big trouble…