Of course! She's the Queen, and it's that kind of story.

Ever agreeable to reasonable royal requests, Catelyn allowed her dress to fall around her feet, then turned to get the kettle. The admiring look she received from the Queen was flattering... even pleasant. And why shouldn't she look so? Cat thought. I've nothing to be ashamed of. We are both ladies, and I was a court beauty in my day, the same as her. Even if, Cat had to admit, it had hardly been to the same degree as she once again got an excellent view of Cersei's breasts, her red nipples hard as little stones.

Cersei watched her pour the water, green eyes glistening, and then briefly dipped her hand into the tub to test it. With a smile, she stepped into the tub, and slowly lowered her nude form into it. The Queen gave a long, contented sigh, and leaned back for a moment. Catelyn stood there, wondering what was to come next, when after giving her arms a few idle scrubs, the Queen turned to look at her. "Lady Stark," murmured Cersei, "I wonder if you would be so kind as to wash my back?"