it's a shame that she got bullied. There are other and more effective ways of communication.
In my opinion she should first have tried to find out whether persons with a nut allergy react to acorns at all. (As a biologist I doubt that very much - too many differences in the respective chemistry).
Secondly, it is not always a good idea to protect allergic persons from allergenes. It has proved to be better for them to get exposed and gradually immunized.
Thirdly, if you cut down all plants someone might be allergic to, you'll be left with a desert.
Forthly, certain plants are known to cause more allergies than others. Yet it'd be a bad idea to extinct or remove them. If children get exposed to them from the very start, they usually don't develop any allergies at all and get a far stronger immune system. Ever heard of a farmer with hay fever?
However, oaks are infamous for rotting inwardly without showing a hint on the outside. Thus, they tend to very unexpectedly drop big branches. If the oaks are older than 70 years (in areas with polluted air I'd say older than 55), it would indeed be a good idea to remove them, in order to prevent accidents. Or at least to give them a thorough inspection every year.