It's typical for boxers to hit a fear period from 6 - 14 months. From a previous post of yours, it seems Gwen is about 7 1/2 months?
Are these fears recent or has she always been scared of these things?
Try and get her out as frequently as you can to expose her to new sights, sounds, and people. Don't overwhelm her, but the more she sees, the less scared she'll be.
Just be sure when she is acting timid, don't try and soothe her. She will view this as postive attention and it will get worse.