My cat has just proved how intelligent she is once and for all. We've got one of those locking cat-flaps, and mostly we lock her out at night.
This will happen no more.
She's worked out that if she head-butts the cat-flap enough times, then the little clip of the locking device will spring out (and this was quite a high-tech cat-flap) and then all she has to do is push hard against it and the whole cover wil come out. ANd so, she can get inside!
My clever little baby!