Sit down and have a heart to heart with her. This is the beginning of the rest of her life and she needs to be an adult about it, and probably feels bad enough about her grades without a lecture. Talk to her about her hopes and dreams and about how she will improve things and become a real person (DH and I are always talking about ways that we will become real people, especially when I'm a worthless pregnant lump on the couch). If she needs suggestions on how to improve her college experience, read ahead.
One thing I wish I knew going into college was how important teachers' office hours are. My last two years I made new friends who I wish I had been friends with all along. I was terrified that office hours were a sign that I wasn't a good enough student (over-achiever here) and I really suffered because of it. Making good friends to do homework with made all the difference for me. Being in classes alone just doesn't work at all.
I went straight to a 4-year university (although I took it in 5 years because I waffled about what I would major in and took some business classes instead of my engineering classes). The semester I got 3 C's and a D just about killed me. I was literally up all night and had to watch "It's a Wonderful Life" to remind myself that I was still worth it. That's when I had friends who told me that "D is for degree" and who weren't serious about learning and blamed everything on how bad the teachers were, and convinced me that all of the classes are curved. I felt horrible when I got the grades that I knew I deserved, and knew that I had to figure things out to improve. Good, hard-working friends make all the difference, IMO. You need a network of friends in every class to study with. It's built-in in high school, at least it was for me in all of the honors and AP classes we were always studying together. It's hard, but it can work.
When I dated and married DH I actually did better in school because he was working for the same thing (a different branch of engineering, but we both had hard majors that involved a lot of outside work). Seeing how hard he worked made me want to be better so that I could be worthy of such an amazing man who has turned out to be a hard-working provider and father. The guys that I hung out with for the years before I met DH weren't as motivated and often convinced me to put of studying to go play with them. Amazing friends, but not what I was looking for.
That's what I learned, and I wish I would have made friends with those people earlier. It changed my life and I wish I could redo my degree. Actually, no, I don't want to go back to school, but I want other people to learn from my mistakes. The people who go to the teacher's office hours, the people who ask questions, and the group of people who look like an exclusive study group, those are the people to make friends with, and they are usually more than willing to be your friend.
BTW, I totally lost my scholarship that semester too, the one I got for being in the top 2% of my class in high school. It happens to the best of us. Remind her that everyone else is looking for friends in college too, and that friends you make in college are much longer-lasting than friends in high school. I just saw one of my old friends from college and wow I just haven't had good friends like I had in college since I left. I guess I need to put myself out more, eh?