Yeah, nah. Brilliant on her part.It was a good pushback... probably.
You suggest she accept him anally, she basically said "you first". IOW, you asked, she told you the price.
Sounds like it could be a place to start negotiation. How much do you want to see her do it? Enough to try it yourself?
(I'm pretty sure the answer is no, so it's a solid pushback... but perhaps not.)