How do I convince my mother to bathe?

My mother is 97 yrs old and hates to hear me talk about having to bathe. She gets very upset with me helping her because I am her son and it is obvious she won't let a man help her with this task. I was able to find an experienced female caregiver though an agency. The lady they sent was like an answer to my prayers. She was very caring and had a very good method to convince her to help her in bathing. I could hear my mother resisting at the beginning, but, she felt more at ease when I heard my mother enjoy the experience. I arranged to have this lady visit once a week. Today, in preparation of this lady's return, I explained to my mom that today was bathing day. She got very upset with me and started to cry and resist the idea. I was told not to give her any explanation in advance of what was to happen, simply, to let her know it was time time to bathe after the care giver showed up, where my mother will have no choice , but to bathe. My question is, is it better to prepare my mother in advance or should I surprise her without notice? I am always affraid to get her upset and ruin the rest of the day...