I have an ex female coworker who invites me out for drinks with one of her girl friends .?

Or gets her friend to set up the date, she is incredibly hot and sexy and flirts continously with me, but at the end of the evening she jumps up and takes a taxi home she is living long term with a guy (appears they get on well but she hardly discusses) it is difficult to chat openly with her pal there, as I said I have the hots for her but am I wasting my time (I have just received an email looking to hook up for drinks from her girlfriend again)????