I will only offer, as T^2 indicated above, to keep it really simple and open, if you do bring it up.
I would suggest only saying something to the effect of, "I am curious about tat-boy. What do you find so interesting about him?"
She may come to any number of conclusions about that question. Then again, she's likely to come to the same conclusions if you said it in 100 words or 1000 words, as well. So no need to waste your breath or keystrokes.
Then, be very liberal in your use of STFU. If she stonewalls, that's your answer (she's not willing to speak about it). If she says anything, listen... validate... and say nothing until you can get away and process that info for at least 48 hours.
There's nothing to discuss. It would be purely for gathering info.