I'd say I'm sorry, I don't feel comfortable doing that as I don't know her well enough and I don't want to wear out the good graces of my employer by sending them a bunch of my friends to them for jobs.
this would work very well.
"I'm sorry, I don't feel comfortable doing that. I don't know D well enough to give her a quality reference."
i would tell her i'd be afraid our boss/es wouldn't take us as seriously and might think we just want to have fun with each other at work all the time and never get anything done, and also that i wouldn't want to feel like i was pushing them into hiring all of my/our friends.
i think it depends on your friend some too. some of my friends would be really defensive about their friends, and some of them would be realistic, if i were to say "well... do you really think she would work though?" in the least snarky voice i could manage. some would get offended, some would be like yeahh you're probably right and catch my drift.
a reference letter doesn't have to be entirely positive.
Get a nice blank piece of paper, and write "She's a bit shit." on it.
Sorry, I don't give references to anyone who I haven't worked with.
I would just say something along the lines of "sorry, I don't feel comfortable giving a reference for people I don't know real well."
Tell her that you take writing reference letters super seriously, and don't feel you know D well enough to recommend her on a professional level.
I would tell her I'm not comfortable doing it, and that I would feel responsible for her and don't know her well enough to put out that risk, etc.
Seriously, if you have any doubts, don't do it. I had a so-called "friend" get hired where I was working (partly on saying that she knew me, without asking me if it was okay to drop my name), and not only did she constantly talk inappropriately to me during work and talk about me in an inappropriate way to coworkers, but she was fired within the month. It didn't reflect well on me, and I wasn't asked back the next summer (it was a summer job during college). It was absolutely horrific.
Pretty much all of the above, no need to get snarky or say mean things. If I was the friend and someone told me they didn't know the third party well enough to write a reference I wouldn't be offended at all..
I would just tell N that you don't feel comfortable writing D a reference/helping her get a job because you don't know her well enough. What I'd actually say is: "I don't feel comfortable writing the reference for D. I only wrote one for you because I'm absolutely certain you will be a great asset to the company and I won't have any problem working with you. I don't know D well enough to make the recommendation, and I don't want to help recruit someone I'm not a hundred percent sure of."
My friend got a mutual friend a job at her work and it was a disaster.
I am sorry I don't have any really 'helpful' advice to offer -- I have few friends and don't have to worry about these kind of things.
If they weren't my friends, I'd take your friend aside and describe to her, point blank, the reasons why you think hiring her friend D would be a bad idea for your friend, yourself, the company and possibly even D themselves.
Try to stand back from subjective judgements and suspicions, and explain objectively that D would most definitely not be the applicant the job is suited to.
If that's impossible? ......I dunno, hold a grudge, dissociate yourself from it, whatever. If you're wise enough to know that D working at the job will not bode well, you've got the smarts enough to find some subtle way of assisting D away from applying.
(: Best of luck.
[I may sound callous or even cruel... ...it's not something that bothers me]
I would just say that you don't know D well enough to write a useful letter
You could try asking her if she thinks she would be a good employee
and ask her to think about how that would reflect on her
ultimately it's up to her what she does, but if you get her thinking she might change her mind
Just tell her you do not feel comfortable as you dont know D well enough. Period. Stop.
Its a respectable, businesslike reason. You already stuck out your neck for someone. Dont do it for someone you dont 1000000% trust to do their job.