Put the plant next to a window or in the garden. Mint can bare lots of sunlight, however some shadow will do too. In fact, mint is a plant that is very mild in the conditions it requires.

Supply your mother mint plant with enough water: unlike other plants, mint needs a lot of water. You do not need to water it the whole day long; It is enough to do it only once a day or twice if necessary. Just make sure the soil is always humid.
A dead mint plant probably hasn't received enough water or sunlight. You can recover such a plant by putting it in the sun and by adding enough water. Be gentle however: a dead mint plant cannot absorb as much water as a grown one.