Is it rude to call your shower greenback?

My bm who is planning her july wedding sent me an invite to her shower. It says right on the invite "so and so's greenback shower". I understand people wanting cash as gifts more than stuff you don't need but I personally think its kind of rude to out right ask for money. Yes people register for gifts, people even register for honeymoons but even those seem to be better than saying "your invited to my shower and I only want cash". I am slowly learning all the etiquette in the wedding world and this just kind of sits wrong with me. Would anyone else find this kind of rude? I also thought you weren't supposed to throw your own shower. Its a jack and jill shower, so everyone invited to the wedding is invited to the shower. I offered to throw her one and told her I would, so it's not like there was no offer. I know usually the MOH is supposed to but she's not having a bridal party.