“My 2 year old daughter was stung by a bee and is now terrified of insects. She will get really upset if any insect goes near her. It is becoming a real struggle as there are insects everywhere!”
I would start by first acknowledging the fact that an insect hurt her. I would then explain that the insect was a bee. I would also go on to explain that the bee was afraid that it would be be hurt by her and that stinging was his way of protecting himself. I would then show her that not all insects are to be afraid of and pick them up and play with them. Good examples are ants, ladybirds and snails.
If you are afraid of any insects yourself (such as spiders) do not let on or you will give her cause to deepen her fear because Mummy / Daddy etc are also afraid.
It will take time, but do persist or it may worsen.
As with all phobias, hypnotherapy may help but I would be hesitant to try hypnotherapy on someone so young.