I organised mine with my mum and sister. I think other people doing it without your input is outdated and can be a bit difficult. I didn't want the cost to fall on anyone else either so I paid for most of it.
Maybe meet up with your sister and BFF and talk it over. I don't think it matters whether or not you have organised one for them previously. I helped organise and finance my SILs baby shower but she wasn't involved in organising mine and that was ok.