You can let your sister take the subway directly to Yaokou subway station, and then take a taxi at the subway station to Huang Qi Jiazhou Square. Very close, no more than 12 yuan. Never take a motorcycle. Very dangerous.
Then you see if there is a smart bus at the airport. You can take the airport bus to Gaoming.
If your sister can't catch the 1 1: 30 subway, you can let her take the airport bus to Fangcun Bus Terminal, and take a taxi to the Historical Square at Fangcun Bus Terminal (there are many taxis from other places, so don't take that, you must take a taxi from Guangdong A). If you take a taxi to the Historical Square from there, you should not surpass 25 yuan.
If it really doesn't work, you can go to the Historical Square with your sister, and get the smart car back at the bus stop opposite the Historical Square the next day. There are many smart cars passing by during the day. Because at night, a girl is really not safe.