Without seeing it, it's hard to know exactly what he's saying, but this gives you some idea of the possibilities.
FRCP Rule 12(b)(6) is one of the most important topics in civil procedure, and one of the most discussed on law school exams.
legal.thomsonreuters.com
Given he's asked for more details, I'm guessing he's saying she's not provided enough facts to make out a
prima facie case against him. Probably a tactic to get her to commit to more detail, in the hope that some of it is likely to be provably inaccurate (because of the passage of time), which he'll exploit to undermine her.