Cash Wedding Gift

I am invited to my work colleague`s wedding as single when all the others have been invited with their husbands/wives and fiances. This colleague knows I have a fiance but still mine was the only one not invited, for some reason. As a small company we decided to fork out money between ourselves and give it as a cash gift. But I feel so offended that I was invited single that I am having second thoughts about forking out money with the others. Do you think it would be rude not to give my colleague any gift given the situation?