Mrs. Jennings *was* the type to match make that is why she said what she did.

Mrs Jennings has had such thoughts in her head because of having two daughters, while for Mrs. Allen such notions are quite foreign.
She took Catherine because she liked her.

I'm quite sure that all she had in mind was enjoying herself, shopping etc. along with Catherine.

Here lies the difference between Catherine and Mrs. Allen.
While for Catherine it was 'the Ball' which was important, for Mrs. Allen it was 'dressing for the ball' which was important.

I think it isn't mentioned if they were ever late after that one time.