I would say you should listen to her but also encourage the language and maths based side. Having worked in a nursery it is extremely frustrating to try to talk to a parent to address any concerns. Almost always the reaction is "no never my child! There's never anything wrong." You will find that if someone has spent a lot of time with a child they will get to know them and if they have real concerns it is worth listening. I have no idea if this is the case with your child but it the parents will never ever listen even when I was trying to be helpful. Try and find an experienced member of staff at the nursery if possible. I know people who have been working in childcare for over twenty years and can immediately spot if something is not right (but as always the parent knows best.)
So my advice is to speak to the childcare practitioner again to clarify exactly what her concerns are and if it is just because he finds it boring or if there are underlying more serious issues here.