If they were purchased using her account then that's what you will need to re-download them. Better would be to purchase your own copies unless you can use Family Sharing.
Family Sharing - https://support.apple.com/HT201060 - "Family Sharing makes it easy for up to six people [different Apple IDs] in your family to share each other’s iTunes, iBooks, and App Store purchases without sharing accounts. Pay for family purchases with the same credit card and approve kids’ spending right from a parent’s device. And share photos, a family calendar, and more to help keep everyone connected."
Set up Family Sharing - https://support.apple.com/HT201088
Sharing purchased content with Family Sharing - http://support.apple.com/HT201085
If you don't see your family's shared content - http://support.apple.com/HT201454