Im going to try and cover all the opinions/suggestions;
to aversion therapy
i was thinking to not tell her to 'tell the other kids off'; its kind of impolite to pull others up on their bad manners is it not?? (she aint perfect herslef!); but maybe she should tell them its 'orrible; because it really is isnt it. I like gnocchis suggestion. Except what HOTC says-what if the kids have medical reasons? although dd herself has adenoid problems which gives her sleep apnoea and she manages
she says that she isnt allowed to move tables once they are sat down; which is fair enough, the teachers cant have all the kids seat hopping. similarily I dont think she could sit on a table by herself;and also why should she sit by herself 
Ive just asked her if she could identify 'quiet eaters' and make sure she sits next to them every day. she said its difficult as some of her friends will rush over to sit next to her, so she often isnt choosing who she sits next to
i dont want to/think I should try punishing her fgor not eating her lunch or threaten her; Ive seen her when in the presence of open-mothed eaters- she proper gags. I think she would actually be sick
houseonthecorner you did scare me a bit
I will look up other things to look out for-i am completely ignorant about anorexia. but good suggestions about focusing on other things in the room-and the nicely eating kids, even if she isnt sat next to them
grockle
i can see that happening
moody i think you were joking, but i think a big screen like lunchbox is a good idea
will lookk at the misphonia link in a minute frownie
demented dd is really slim and really active; Id be everso worried about her not eating for that length of time
re objections to the word 'disgusting'; it may be that people cant help eating like this for whatever reason; but there is no getting away from it -it is disgusting!!
so i think on reflection; she doesnt have much control over who she sits next to. I dont want her to have to sit on her own. Im going to get her a big lunch box to hide behind; tell her to ask other kids to try to eat more quietly/close their mouths; teach her some distration techniques. I am also going to talk to the teachers and see if they can do circle time or be more vigilant at lunch time and encourage kids to close mouths etc. I dont care if you do think thats a bit 'nanny state'- its a primary school!
thanks for all your input-off to find out what 'misphonia' is!