Many thanks to Loryn Jenkins who answered my question about the origin of the – seemingly silly – expression “to rabbit on”:
To rabbit on is to carry on talking, often about trivia and to
the annoyance of others. The saying comes from rhyming slang. Rabbit and
pork stew used to be a popular stew. "rabbit & pork"=talk.
[source]So rabbiting on isn't talking nonsense, but talking incessantly. Which
means that it does make sense for you to describe her as rabbiting on;
which, alas, destroys your double-negative. You're in a bind---unless you
accept the etymology.
This might seem strange ... but I'm genuinely thrilled to know the answer. It had been bothering me.
