I find it odd that in any of their previous meetings Mrs. Smith never once mentioned to Anne that she knew Mr. Elliot - even if it was to say: "I once knew a Mr. Elliot, I wonder if he might be a relation of yours?" or some such thing. She did not need to tell Anne all, but keeping from Anne for so long the fact that she knew him strikes me as odd.

Also a bit of a stretch to me that once she does tell all, the timing could not be better for Anne, and Anne believes her entirely.