My brother recently became engaged and his fiance whom I don't know and have never met has asked me to be a bridesmaid. While I do appreciate her including me, I feel it would be more appropriate for her to include someone she is closer to. Or, it could be important for my brother to include me in the wedding. However, I feel she might have asked me just to be nice and perhaps get to know me a bit. The wedding is not for a year and my job is not predictable enough to commit to many functions like showers etc.
I don't want to negatively taint her wedding experiance by saying no but I don't want both of us including me in the wedding just to be nice.
Approach this as you would anything else--be honest. If you don't feel comfortable with it, politely decline using any excuse you wish to use. It is very true that she should have someone close to her in this position.
You could also offer to help with the activities in the future even though you are not an attendant. This could bring you two closer.