Hi Shannon,
Do you always give her a super special treat whenever she does her business in the right place? They have to have some motivation to pee where you want them to, or else they don't care where they pee - the release of the bladder is enough reward for them, no matter where they happen to do it. So you have to give them something BETTER than just that sweet feeling of release, lol.
Also, dogs will decide where their "den" area is, and then anywhere else that is not "den" is considered by them to be a good place to pee. We have to help them realize that OUR HOUSE (or bus, whatever) is their den, and give them their own designated "non-den" place for peeing. Expanding their "den" slowly instead of too quickly helps, and catching them in the act, stopping them, and making them finish up in the "correct" place and treating them immediately afterward helps them to decide where the right place to pee/poo is. This last part is the part that takes the most work - you've gotta watch 'em constantly. And that's why we on the YT Potty Log consider ourselves "in the trenches" lol. Welcome to the ranks!
Good luck!
Lauren & Nikko