How does she drive with one leg?

She is seen driving over some of the most treacherous roads in the Johto region, along a route prone to freak twisters, sudden downpours and presumably landslips. Because of this, she would need to have a foot over the break the whole time so she can stop as quickly as possible when an incident occurs. The split-second it takes her to remove her one leg from the accelerator to switch to the break could mean the difference between life and death in conditions like these. Let's not forget that the bus is shown to be a manual, further requiring her foot for frequent gear changes.