Just talk to her about what happened and let her know it's not a big deal, make her comfortable, etc. Once the ice is broken, you never know what will happen. She might feel totally relieved and liberated, and you will, too! No need to be sneaky about it.
A few years ago, my wife's friend stayed with us for two weeks. One night, I saw her topless running from the shower to the bedroom. After talking with her, the rest of the time she would dry her hair topless, etc, with the bathroom door open while my wife and I talked to her.
It was actually a stress relief, since having her living with us was otherwise a disaster.
