give her a chance, she might surprise you! Who knows, it may become something that you both enjoy together.
I enjoy riding by myself also. I find that I get a much better workout by myself but that doesn't stop me from riding with my friends. They drive to the trailhead and I ride there. The trailhead is at the top of a big hill, so I get a good workout heading up there. I also commute every day. This allows me to get a few more miles in on days that I ride with my buddies. Riding with friends is a different kind of fun than riding alone and I like both kinds.