I have always loved to sleep 9 or 10 hours. I frequently fall asleep around 8pm or 8:30. I am more of an early riser type of person, too. It is much easier for me to get up early than stay up late and I get VERY unhappy if I'm forced to stay up too late.
In my personal opinion, the Primal Blueprint and Paleo both make a big deal about getting enough sleep. This has been liberating for me to recognize that sleeping as much as I feel is right for me is not only good for me but within my rights to do without guilt.
I would consider your girlfriend's early to bed routine to only be a problem if it is a problem for HER. And I would not consider that to be evidence of "low energy."
Now, if she has no energy at all during the day, then maybe that is a problem. But she's going to have to be the one to address it. Getting some low-level exercise like walking out in the sunshine and eating nutrient dense foods, avoiding sugar and flour, should help, but not everybody is a bounding ball of energy, either. All the exercise the Primal Blueprint fitness program asks of you would probably kill me if I did every bit of it on the schedule that is recommended. And I'm someone who walked the length of the US. I don't really consider walking to be a lot of exercise. It's all that running around chasing balls and jumping up and down kind of stuff that kills me. I have always despised that sort of thing.
Female, 5'3", 50, Max squat: 202.5lbs. Max deadlift: 225 x 3.