Does this seem like a reasonable request from my GF?

My GF and I love to go to the beach to hang out. She loves to wear "small bikinis" and I love it as she has the body to show them off. Yesterday she asked me if I would wear a brief style suit to the beach instead of my board shorts (I own several speedos as I am on the swim team at school). I said I would thinking that she meant one of my suits. However, as soon as I said yes she handed me a bag that contained what in effect can only be described as a male string bikini. I balked at wearing it but she is now saying I agreed to it and I would be breaking my word. The suit does cover everything although just barely and technically she is right I did agree. Should I actually wear it and if so and I did wear it once to the beach would that be keeping my word?