hallo everybody!jess has developed a disinclination to be stroked by people she doesnt know,if they approach her,she moves away,and on one occasion,when someone ignored that and tried again,actually snapped.nowadays i warn people  off.I can see where shes coming from,I wouldnt like it either!shes fine in class,during   "controlled greeting",have i got a problem,shouldI be doing anything other than avoiding the problem?oh,and shes brilliant with anyone she knows,plays nicely with the kids.thanks in advance!

have had the same problem with my TT apart from she doesn't snap, just tries to get away and barks if they insist on approaching her.
Thankfully after a year or so she is a lot confident. my problem was because she came from a kennel and had little socialization etc.
Anyway they only way forwards after a lot of advice from other doggy owners was to start from scratch and firstly not put her in a situation where she would feel scared ie on meeting people i would ask that they didn't give eye contact or try and touch her, when she became more settled with that i gave anyone or people out walking i bumped into a tasty treat to give her but for them to drop it on the floor and still not look or touch her. The thing is to get them to associate nice things with anyone they meet and i've learnt you can't rush this but only take it at their pace, in my case it took along time but that doesn't mean it will with you.        
i still ask people who come to our house to ignore her until she comes to them and by doing this she has made the first move to them and is a lot more relaxed.
i too go to classes even though my dog is really well trained now but it keep the contact with other dogs and people going. i also asked a few at my classes to walk with us so my dog got used to other people being around us.
If my dog is nervous i don't try and stroke her but just ignore her,  other wise they seem to get more stressed because your rewarding this behaviour.
i'm know dog expert but these steps have worked well for me so i hope they will for you. 

As she is fine with controlled greeting I would use a command that tells her she is going to be touched by someone as in 'say hello'.

Otherwise tell people to ignore her until she approaches them.

if they approach her,she moves away,and on one occasion,when someone ignored that and tried again,actually snapped

Then this person completely ignored what your girl was telling her ... which was basically I don't want to say hello.

Read Suzanne Clothier's article "He just wants to say hi" - essential reading for everyone with or considering having a dog!

http://flyingdogpress.com/content/view/42/97/

I don't think you've a problem at all.

I wouldn't be overly worried, she is showing clear 'I'm uncomfortable with this' signs, and you are aware.  It isn't like she is unpredictable.  What breed is she?  Not all breeds are happy go lucky with everyone, some are meant to be aloof with strangers, but excited to see those they know. 
I own a breed that is naturally aloof with strangers, they will allow strangers to pet them, but will always have a 'do they have to' face.  I socialise mine early and go to two classes a week minimum in the early stages so they welcome this attention.  This is achieved by letting strangers give a treat followed by a fuss, gentle encouragement from you, and working at the dogs pace.  My girl will actively seek people to say hello to on walks, is all sweetness and light until all pockets are thoroughly checked.  If they dont have anything she will march off with a disgusted look on her face!
You are aware your girl has this issue, so in the first instance you can help her avoid such situations.  I would get to an obediance/ring craft lesson and at her own pace allow her to take treats from other owners.  Dont force it on her, she will soon learn that approaching people will give her a yummy reward.  And if she doesn't take it there are several other hungry mouths ready to take her place.  I'm a firm believer of dogs learn far more at a much quicker pace by watching how other dogs behave than what we can ever teach them.  (But obviously you are there to help!)

thankyou,i really enjoyed reading that link and it made so much sense.Shes actually been like this since she was spayed,when she developed fear of the vets,nurses,and i suspect she looks at anyone she doesnt know,with mistrust,now.I dont know if collies are classed as an aloof breed,I cant say any of mine have been particularly friendly,either to dogs or people(not aggressive,just not bothered!)i liked the idea of giving people a treat to give her,too.I walked round a car boot with her today,for a new experience,and she was fine.Sometimes people are so quick ,though,and have practically got their mitts on your dog before you can get your brain in gear.I think I feel reassured now,thanks to you kind people.I think she l be ok,as long as I keep my wits about me!Thanks everybody!

just to confirm that the stranger=treat does work well long term, my last GSD had the attitude that 'mummy told me not to talk to strangers' so I always had a pocket of treats, he didn't get to the stage of 'mugging' people but at least stopped backing away and worrying.

ps, tried him in a smallish breed show at 6 mths and 1 week, he stood well, then the judge took a step towards him, he was suddenly transported to behind my legs - peering round from behind my knees...... :-D did finish 4th out of 5
Chris

just what you needed!bless him!