Q.What is the white stuff on the soil of my spider plant?
Someone told me I needed to re-pot it, Is this true?

Certified GKH Gardening Expert
Not necessarily. This is fungal mycelium, which in most cases is a good thing.
It does, in this case, indicate that the plant is being overwatered. Spider plants are very drought tolerant, preferring dry soils. They can go very long periods without water.
If the soil smells fresh like soil, or like mushrooms, then you are fine. If it has a sulfur smell, however, then you will want to re-pot the plant.
Here is an article that will help you to give these the most proper care: https://www.gardeningknowhow.com/houseplants/spider-plant/spider-plant-care-gardening-tips-for-spider-plants.htm