Is it okay to aska bridesmaid to "step down"?

Okay so I've actually asked a couple of questions about this bridesmaid, but the gist of it is since we both became engaged(me a couple months before her...our fiance's actually bought our rings together...they're best friends and each other's best mans) Anyway their wedding is 5 months after ours and I'm supposed to be in hers as well...this was all fantastic and I was really excited until she startedto change. She gets mad at me about my wedding because it's "fancier" than hers...to the point where I cannot talk to her about anything pertaining to my wedding, which I was upset about but I figured oh well we can just talk about hers instead its all good, but we've just grown apart, shes miserable now when she used to be so happy and social. She also recently informed my fiance she probably wont be making it to the shower and although I know i'm not supposed to know any details about the shower my sister let me know she also never contributed money towards it( all the maids decided....