Although she only stayed for two days, her bag was huge and pretty heavy. Still, we used the Citybikes to get to the Tunnel for breakfast and then to my place, to go shopping and so on. She actually owns two bikes herself, but both of them are mountain bikes for training purposes. Still, she didn't have problems to adjust to the single-speed and new three-gear Citybikes.
The only thing that caused a bit of confusion was the coaster brake as she generally uses two handbrakes. Well, it wasn't a huge problem. Only once we had a minor accident ...
I was riding in the front and stopped rather fast in front of a crosswalk to let a family pass which my sister (riding behind me) didn't see. Having problems with the brake and sliding as well (it was pretty cold and raining, much different to the days before), she hit my rear wheel and fell. Well, speeds were low and nothing happened. She'll get away with a bruise on her left thigh. Moaning is not something she would do anyhow, she immediatly laughed about her faux pas. Such things happen, nothing to be afraid of. I also fell a few times when braking full on wet/slippery roads, but that's also how I learned how to deal with such conditions :-).
I guess my sister wouldn't consider herself brave just because she cycles in the big city without worrying much. But many of my friends here often told me that they would never cycle in Vienna because it is so dangerous -- even the ones that grew up here and are very familiar with a lot of busy traffic. Well, don't be such wimps, look at my little sis!