Wouldn't it depend on just how poisonous/corrosive Adamantium is? I was under the impression it was on the sort of level of something Arsenic (although maybe significantly more potent), it will ultimately kill you, but it would take a fairly decent amount of time. HOWEVER I don't read the comics, and just know slightly more than someone who just watches the movies/animated series, so if I'm wild wrong, please don't impale me on extending/retracting claws...
Since it is internal, she wouldn't have many (any?) pain receptors, and the moment she is out of Null's aura, her healing factor will kick in and purge the poison/corrosion more quickly than Wolverine, not that I would expect Logan to ever be having sex with Null.