P.K.
I would be out all day every day! Kids need to be exposed to the outside world and yes germs are good for kids. They need them. If she was premature, then very early in you need to be cautious. Was she a preemie?
Join a music class or a gym class expose her to other kids. Go to the library, a horse farm. Hopefully by the time summertime comes she will be able to enjoy herself and not be so fearful. Good luck. While you are out, let her get dirty. There are many benefits to that.