You can usually expect about 12-15 hours of wear from a pair of pointe shoes. To get the most out of that lifespan, follow some basic care principles. Because they are made of natural materials, most pointe shoes break down when wet.
Use a mesh bag outside her dance bag to carry her shoes after class. (Some dance bags come with external mesh bags for this purpose.)
Remove toe pads immediately after use and store them separately from her shoes. Shoes must never be squashed, and they should be set out to air-dry thoroughly between classes, ideally for at least 24 hours. When dancers wear pointe shoes daily, they often alternate pairs so that each pair has time to dry completely before being worn again.
Read more about replacing pointe shoes when they no longer provide proper support.