She works in a kindergarten where they serve pork once a month

Praise be to Allah.

If there are Muslims among these children, then you should not approve of the kindergarten offering this haraam meat to them; you have to make sure that the administration knows that they should not give this food to the Muslim children. 

But if these children are not Muslim, then they regard it as permissible to eat pork and the Muslims have no authority over them in their own country. 

In this case, it is sufficient for you not to help with this haraam action or be present when this food is served. In that case it is permissible for you to remain in this job. 

And Allah knows best.