Panic!

So a thought, I recently had a situation where a very attractive and fairly busty woman, in efforts to check her phone, reached around behind me and her breast was pressed up against me. How does one react to this? You try to not make a big deal of it but at the same time you don’t want to suddenly pull away. I froze, like a stone statue lol. But what else can be done? What SHOULD be done? And it wasn’t the first time she’s done it. Every time I freeze, an awkward situation indeed.