Siamese kitten

Question
Yesterday, my kitten, who is 7 months old and in good health, came in from the garden and appeared to have something in her mouth that she was trying to shake out.Later, her mouth seemed swollen on one side. She vomited four times, at about half-hourly intervals, until there was just clear liquid. She has been extremely lethargic since, just lying around sleeping. Normally she is hyperactive. Should I take her to the vet?
We live in France, and as it's winter, we don't have many stinging insects around. We don't have any poisonous chemicals in the garden either.

Answer
I would suggest it safest having her seen by your veterinarian due to the swelling and vomiting.  I am sorry that I do not know your area very well as to its insects etc but spiders, bees/wasps, certain ants and many other creatures could bite or sting and cause swelling and perhaps a toxic reaction such as the vomiting and the lethargy.  The appearance of trying to shake something out of her mouth could have been a creature or been attempting to "shake away" a sting.  

Best of luck to you and your kitten.  Hopefully she will be back to her hyperactive self very soon.