Thanks Robbin for bringing this up. She is so sweet that I do love her tenderly. :-) We've been set up in the earlier chapters to see how ridiculous she is with her matchmaking and gossip; but when they get to London, we learn of her true goodness.

I actually made a page of notes on the good qualities of Mrs. Jennings.

She's active and not just in gossiping.
to Col. Brandon when they arrive in London ch. 26
"I am monstrous glad to see you -- sorry I could not come before -- beg your pardon, but I have been forced to look about me a little, and settle my matters; for it is a long while since I have been at home, and you know one has always a world of little odd things to do after one has been away for any time; and then I have had Cartwright to settle with. Lord, I have been as busy as a bee ever since dinner!

She was an affectionate wife, and is very self effacing and humble
Well! I was young once, but I never was very handsome -- worse luck for me. However, I got a very good husband, and I don't know what the greatest beauty can do more. Ah! poor man! he has been dead these eight years and better.

Her concern for Marianne is so sincere. Yes her gossiping does damage but her heart is always in the right place.
ch 29. I hope, from the bottom of my heart, he won't keep her waiting much longer, for it is quite grievous to see her look so ill and forlorn.
She almost sinks from the shock and concern for Marianne on learning that Mr. Willoughby is engaged to Miss Grey. But she is so practical too.
Ch. 30 he has no business to fly off from his word only because he grows poor, and a richer girl is ready to have him. Why don't he, in such a case, sell his horses, let his house, turn off his servants, and make a thorough reform at once? I warrant you, Miss Marianne would have been ready to wait till matters came round.

And who couldn't love her for this?
ch. 34 The same manners however, which recommended Mrs. John Dashwood to the good opinion of Lady Middleton, did not suit the fancy of Mrs. Jennings, and to her she appeared nothing more than a little proud-looking woman of uncordial address, who met her husband's sisters without any affection, and almost without having anything to say to them;

When John Dashwood comes to talk about the Edward and Lucy engagement, I love how she speaks up
"Then," cried Mrs. Jennings, with blunt sincerity, no longer able to be silent, "he has acted like an honest man! I beg your pardon, Mr. Dashwood, but if he had done otherwise, I should have thought him a rascal.
You can almost sense some anger or tartness after he tries to explain some more.
"Well, sir," said Mrs. Jennings, "and how did it end?"

She seems to sincerely love Elinor and Marianne (in spite of the way Marianne treated her). When she brought in the letter to Marianne from her mother, thinking what comfort she is bringing her, it is so wrong and it pains me that Marianne considered it "cruelty" (ch. 31). Mrs Jennings loves them as her own daughters I think.
ch. 39
"Ah! Colonel, I do not know what you and I shall do without the Miss Dashwoods;" ... Lord! we shall sit and gape at one another as dull as two cats."