It is probably safe to say that she wasn't Force-sensitive, mainly because it further adds to the legend of Anakin, but I don't think it is ever truly established.
As far as your second question pertaining to the possibility of a non-Force-sensitive producing a messianic Force birth, The Darth Plagueis novel makes two things clear relating to midi-chlorians:
Midi-chlorians exist in all lifeforms, this is shown when Plagueis manipulates King Veruna's midi-chlorians (who did not possess enough of them to be considered to be Force-sensitive), which in turn slowly killed him. The other item that the novel establishes, is that Anakin was born as a direct result of midi-chlorians thwarting Plagueis' attempt at tipping the balance of the force towards the dark side.