knows she is working or not, maybe just relax; so you should not feel obliged to stay late, since you work 5 days a week, she probably only works 3 days a week
My boss also stay very late until 7 or 8, but he came late too...so I just go when it's time off
My boss also stay very late until 7 or 8, but he came late too...so I just go when it's time off