Vomiting can be an indication of something more complex, but I would suspect that if this only occurs after feeding your bitch, then it is probably a perfectly normal behaviour.

Regurgitation would more aptly describe the habit.

Labradors are prone to bolt their food, especially if they are eating in competition with others and this behaviour need not cause alarm. However, if regurgitation continues, and not just once after each feed, then a veterinary examination is required to rule out any possible obstruction or narrowing of the oesophagus.

I have found teaching a dog to eat more slowly or in controlled stages will stop this habit. I always make a dog sit for its food, and then eat on command.

If it begins to bolt the food down, I immediately make it stop eating and sit until I can see it has relaxed, when it is allowed to eat a little more.

This type of training also stops a dog bloating and does wonders for discipline and control.