You do not
You do not know what is going on in her head when she is presenting herself towards you. Sometimes it is fun, sometimes lust, sometimes erotic feeling maybe and sometimes she may even hate you for what YOU are doing ! So do not never ever ask her what she is thinking now or even feeling !!
Terrible mistake. Just let her mood flow. Use it. It is her expression and as part of the emotional layer it will help to build up a strong expression for you and your picture.
Olympus E-5, ISO100, Sigma 30 mm, f1.4, 1/125 second and again the single flash bounced again in the usual way :)