my bitch has 12 3 day old babies and has been the perfect mum. the only problem is she looks absolutely shattered and is getting out of the whelping box now and leaving the pups on their own inbetween feeds.  she is just totally exhausted and just sleeps and looks miserable.  she is eating ok and drinking plenty.  does anybody have any tips on getting some life back into my poor girl.  are there any vitamins that will help but will not affect the pups or any particular kind of food that someone can recommend. any advice will be appreciated

The pups are old enough now to manage without her for a while between each feed, as long as the whelping box is warm enough. Is Wilma going out for walks? Often a change of scene and some fresh air and exercise helps them.

she is getting out but only into the back garden, i am concerned about her coming into contact with other dogs. 

As long as her vaccinations are up-to-date she's at no risk.  My bitches have always demanded to go out for walks as normal after about 4 days, and we've never had any problems, but of course that's your decision, and you must do what you're happy with. My breed's bigger than yours, and just running in the garden wouldn't give them enough exercise.

Do you take her into the sitting-room to cuddle while you watch TV, etc?

yes, she is the most spoilt dog. this is why it is upsetting to see her like this, she is usually so happy and playful!

As long as she's getting good food, plenty of liquid, and rest, she should be fine. If you're seriously worried get the vet to come and check her over. But having a litter is exhausting for them, especially in the time they're growng before weaning. At about 3 weeks she'll most likely be eating about 4 times her usual amount just to feed herself and pups.