While in the car, Mina's heart began to race. It was not another panic attack, but she had come to the sudden realization that she was going to be alone with Luna and her, most likely rich, friends. This meant that she would probably meet with Miss Lisa at some point during the night.
In the dark about their relationship, Mina wanted to know how close the women were. There was a good chance that Luna had only invited her in order to allow Lisa time to mentally torment her. She needed to figure it out, but she did not want to be too forward, and make her companion suspicious.
"Luna and Lisa are similar names. Are your families close?" Not surprised that Mina was worried. Luna answered the indirect question directly.