I thought you were asking us how to get a friend to, "talk less politely." lol. As if you thought she was too polite.
I don't know, good question. I have similar problems. The best way, I think, to resolve this type of problem, is to insert a very blunt, but stabbing, sort of, 'hint.' This type of hint, is the kind, the receiver, upon hearing it, can't be sure whether you meant, 'A,' or, 'B,' but is filled with so much doubt about the intensity of your sincerity, that it becomes a bit disquieting; and upon hearing this hint, a natural silence ensues for the receiver, for a lingering introspection will have developed, as to whether or not what you meant was a bit painfully and strikingly true, or not.
I don't know how you deliver such a remark though. Such procedures arise spontaneously, among the wise, I believe...
An image of two young women walking in the park, comes to mind...
One is relentlessly vomiting words to the other's growing disdain, as she watches even the crows fly away in annoyance. The sun is setting on a snowy day, in the park, and she finally gives up, and realizes she couldn't care one way or the other if a cougar suddenly jumped out from nowhere and choked the words out of her loud mouth with a bite to the neck. Then suddenly, a calm comes over her. She doesn't know from where; but, suddenly the snow covered trees look strikingly beautiful in a way she hadn't noticed before. She pans her vision around as she feels the snow crunching beneath her boots, giving her tiny sensations of joy and satisfaction, who's origin she couldn't know. She looks over at her friend in pure awe. She notices the little lines in her face, the rapid movement of her mouth, and how utterly unaware of her surroundings she is. She imagines a beaver busily gnawing away at wood to carefully craft a damn. She laughs to herself a bit, as she notices the steam rising from her friend's mouth, with every word, and breaks into an uncontrollable fit of laughter. Her friend, stops, and turns to her, looking a bit puzzled, "what are you laughing about?" She speaks with an air of slight annoyance, as if maybe she wasn't getting her much deserved attention.
Her friend, chuckles a bit more, and says, "keep talking, I want to see all that steamy, hot air come out of your mouth; it's sooooo cool!" Her friend doesn't say a word for a moment, then says, "what?"
"I was just watching all that hot air coming out of your mouth, it looks soooooo pretty!" "Say something, please!"
Her friend replies, looking a bit puzzled, and slightly disheartened, "I don't know what to say..."
Then she takes in a deep breathe, exhales slowly, and meaningfully, and says, "doesn't that look neat?"
Her friend, having little idea what she's getting on about, replies, "yeah, I guess so."
For a few moments, she gets a few moments, of that precious silence she was seeking. Eventually her friend, starts talking again, mindlessly vomiting up words; but, she finds she isn't so bothered by it any more. She watches it, studies it, to the point she can't even decipher what she's saying anymore, and is just noticing the rhythm and the changing pitch; how it goes up, down, moves in this direction and that. Before she knows it, they have walked several miles, and several hours have passed.
Her friend, suddenly, goes quiet. She doesn't realize it at first, and they keep walking in silence. Suddenly her friend says, "I think I better get going." But, she doesn't hear her. She heard her, but, it just didn't register, she long since tuned out all the talking and was absorbed in the cold, dark, wintry splendor. "Angela," she says again. "I think we better get going, it's getting late."
"Right," she quickly replies, "sorry I was just day dreaming." They walk back to their cars in silence and say their goodbyes. It had been a bit over three hours and she realized, her friend must have talked herself out.
As she was driving home, Angela just decided to make sure she had other things to get busy with, in the future. She didn't feel quite right making up white lies; so from then on, she just managed to, some how, at the right time, be a bit too busy to spend too much time with her friend. Eventually they slowly drifted apart; but, would catch up, every now and then, from time to time...