Small reliable car with good gas mileage, my choices would be Mazda or the Ford Focus both come in yellow.
I did a quick search and there are a few out there, I don't know your exact Zip Code so I used 94039 for the mountain view area, punched in yellow and allowed 100 miles ratio through autotrader.com
Yellow is cute and a nice choice for a young lady in these compact cars,,, best part is you can spot her easy if she does the bar hop to late,,,lol
PS,,, If you are having problems using the provider,,,post your Zip