Bridesmaid Backing out via email!so p**sed!

So FH's cousin and one of my best friends just emailed me to tell me she cant be a BM because her and her family are moving in from Orlando to another part of Florida in August!!! I am so mad!! Not only did she tell me this via email but she made sure to emphasize that 'she knows we will be upset and she will try her hardest to be at the wedding but there is no guarantees and to not be mad at her!' This is after WE (me and FH) paid for her dress 3 months ago!!! I asked her to be a BM over a year ago and I always had the sneaking suspicion that she would pull something like this! Mainly she has issues with money (which is why we bought her dress) and we told her all she had to worry about was getting here and she cant even do that! And to email me and tell me she didnt want to stress me out is insane

She is the 3rd person to back out of the party! First it was FH's aunt's boyfriend and his son (because the aunt and boyfriend broke up) and now this!!! I cant believe how disappointing everyone is!!! SAD!!!And what makes me even more hurt is that this friend is the sister of my best friend who died from cancer and we grew closer since then and for her and her family (because they might not make it either) is just awful!!!!