Bridal Shower Ediquette

I am trying to plan my sister `s(Shae) wedding shower however, am having trouble with one bridesmaid. Shae is getting married on September 20, however she lives 5 hours away from the town where we grew up. She has twin boys who are 4 months old and do not travell well.She is back home visiting for three weeks and I would like to have her shower within the three weeks. That way she would not have to travel with the babies anymore than possible ( our cousin is getting married the weekend before Shae`s wedding and she is coming home for that too). As it sits right now, Shae will be coming home three times withing the next five weeks (one for Tara`s wedding, her own wedding and her stagette). I think that it is a lot for her to do with twins, and the stress of long distance wedding planning. There are five bridesmaids, and of all of them only one has a major problem with it..she wants to plan everything for Shae`s wedding, and thinks that I should back off (Iam the maid-of -honor) because I am Shae`s sister and it is rude for the sister of the bride to plan a shower. My quiestion is this..IS it rude for me to plan Shae`s shower (I am including the other bridesmaids) and is 5 weeks to early for the shower considering the distance factor?