47hp more than enough power to start on and it will easily keep up with traffic with both you and your girlfriend on that back. You will notice it is always riders to be who have concerns over weight and being able to keep up. It is rare for experienced riders to mention this and when they do, it is always the 250 class.
For comparison, madjak and his bike combined weigh 655lbs with 47hp.
Me and my scooter weigh 713lbs with 40hp.
In 16,000 miles of riding I have rarely wished for more power as I leave cars in my dust without even trying. The only time more power would be nice is on long straights at higher speeds. That would be nice to have but is not essential to have. In all honestly I have started eying the little Ninja 250 as a second bike. I think something that light would be hoot to ride on country roads. Riding in straight lines is boring and I have no interest in 100+mph. You don’t have to look far for find very experienced riders having a blast on that thing and shaming the larger bikes in the corners.
Oh and in case it’s not obvious to you, you want to wait a long time before putting your girlfriend on the back. Having a passenger completely alters the dynamics of a bike and you should be experienced riding alone before even attempting to do that.